Flight Effects on Noise Generated 

by the JT8D Engine With Inverted 

Primary/Fan Flow as Measured 

in the NASA-Ames 40- by 

8@Foot Wind Tunnel 

Frank G. Strom 

CONTRACT NAS2-9302 

JUNE 1978 
, .- 

TECH LIBRARY KAFB, NM 

NASA Contractor Report 2996 

Flight Effects on Noise Generated 

by the JT8D Engine With Inverted 

Primary/Fan Flow as Measured 

in the NASA-Ames 40- by 

86Foot Wind Tunnel 

Frank G. Strout 

Boeing Commercial Airplane Company 

Seattle, Washington 

Prepared for 

Ames Research Center 

under Contract NAS2-9302 

National Aeronautics 

and Space Administration 

Scientific and Technical 

Information Office 

1978 

--- 
.___ _.--_- _._____.. -...-.- - - -. 
I -. 

CONTENTS 

Page 

1.0 SUMMARY ....................................................... 

2.0 INTRODUCTION. ................................................. 

3.0 ABBREVIATIONS AND SYMBOLS. ................................... 

4.0 TEST DESCRIPTION. .............................................. 

4.1 StaticTest .................................................... 

4.1.1 Facility Description. ...................................... 

4.1.2 Engine Description ....................................... 

4.1.3 Test Hardware Description ................................. 

4.1.4 Instrumentation ......................................... 

4.1.5 Acoustic Data Reduction .................................. 

4.1.6 Test Procedure .......................................... 

4.1.7 Test Conditions. ......................................... 

4.2 WindTunnelTest .............................................. 

4.2.1 Facility Description. ...................................... 

4.2.2 Test Configurations. ...................................... 

4.2.3 Instrumentation ......................................... 

4.2.4 Acoustic Data Reduction .................................. 

4.2.5 Test Procedure .......................................... 

4.2.6 Test Conditions. ......................................... 

5.0 DATA ANALYSIS ................................................. 

5.1 

5.2 

5.3 

5.4 

5.5 

5.6 

AnalysisTechnique ............................................. 

5.1.1 Noise Source Locations. ................................... 

5.1.2 Wind Tunnel Reverberant Field. ............................. 

5.1.3 Background Noise. ....................................... 

Baseline Analysis. .............................................. 

5.2.1 Static Data Analysis ...................................... 

5.2.2 Wind Tunnel Data Analysis. ................................ 

Inverter Analysis. .............................................. 

5.3.1 Static Data Analysis ...................................... 

5.3.2 Wind Tunnel Data Analysis. ................................ 

Internal Mixer Analysis. ......................................... 

5.4.1 Static Data Analysis ...................................... 

5.4.2 Wind Tunnel Data Analysis. ................................ 

Inverter/Plug Analysis. .......................................... 

5.5.1 Static Data Analysis ...................................... 

5.5.2 Wind Tunnel Data Analysis. ................................ 

Inverter/Mixer Analysis. ......................................... 

5.6.1 Static Data Analysis ...................................... 

5.6.2 Wind Tunnel Data Analysis. ................................ 

1 

3 

4 

7 

7 

7 

7 

8 

8 

9 

9 

9 

9 

9 

10 

10 

11 

11 

II 

12 

12 

12 

13 

14 

15 

15 

15 

16 

16 

17 

20 

21 

21 

22 

22 

22 

23 

23 

24 

. . . 

111 
CONTENTS (Concluded) 

Page 

5.7 Comparison of Static and Flight Noise of Inverter Configurations .......... 25 

5.7.1 OASPL Directivity Comparison. ............................. 25 

5.7.2 PNL Directivity Comparison. ............................... 25 

5.7.3 EPNL Suppression Comparison. ............................. 26 

5.8 Engine/Inverter Duct Performance ................................. 26 

5.9 ModelResults ................................................. 27 

6.0 CONCLUSIONS ................................................... 29 

6.1 Basic Inverter ................................................. 29 

6.2 Inverter/Plug .................................................. 29 

6.3 Inverter/20 Lobe Mixer. ......................................... 30 

6.4 Model Results ................................................. 30 

REFERENCES........................................................ 31 

iv 
FIGURES 

No. Page 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

Static Test Installation, Inverter Configuration. ........................... 34 

Test Configuration Schematic. ........................................ 35 

Primary/Fan Flow Inverter, Exit Station. ................................ 36 

Test Installation in 40 by 80 Wind Tunnel ............................... 37 

Inverter/Plug Configuration. .......................................... 38 

Inverter/20 Lobe Mixer Configuration .................................. 39 

Inverter/20 Lobe Mixer Configuration with Acoustic Shield. ................. 40 

Multiple Sideline SPL Directivity JT8D-17R Engine with Inverter 

Configuration ..................................................... 41 

Determination of Noise Source Location, Inverter Configuration ............ 44 

Noise Source Location versus Emission Angle, Inverter Configuration .......... 47 

Noise Source Location Correlation for Inverter Configuration ................ 50 

Near Field SPL Adjustment. .......................................... 54 

Reverberant Field Spectra for Inverter Configuration. ...................... 55 

Comparison of Free Field and 40 by 80 SPL Directivity, Inverter 

Configuration.. ................................................... 57 

Relationship of Reverberant Field SPL to Peak SPL, Inverter Configuration ..... 63 

Comparison of Reverberant Field Spectra, Inverter Configuration ............. 64 

Tunnel Background Noise Spectra. ..................................... 65 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Baseline Configuration .............................................. 66 

Velocity Exponents for OASPL and PNL, Baseline Configuration ............. 68 

Static and Estimated Flight EPNL Characteristics, Baseline Configuration ....... 70 

Comparison of Near and Far Field Spectra, Inverter Configuration. ............ 7 1 

Comparison of Near and Far Field OASPL and PNL Directivity, 

Inverter Configuration. .............................................. 74 

Comparison of OASPL versus Primary Velocity, 30.5 m and 3.05 m 

Data-Inverter Configuration .......................................... 78 

Comparison of PNL versus Primary Velocity, 30.5 m and 3.05 m 

Data-Inverter Configuration .......................................... 80 

Comparison of Baseline and Inverter Spectra: NPR = 2.2. ................... 82 

Comparison of Baseline and Inverter Spectra: NPR = 2.1. ................... 84 

Comparison of Baseline and Inverter Spectra: NPR = 1.8. ................... 90 

Comparison of Baseline and Inverter Spectra: NPR = 1.6. ................... 92 

Comparison of Baseline and Inverter Spectra: NPR = 1.4. ................... 94 

Comparison of Static OASPL and PNL Directivity, Baseline versus Inverter ...... 96 

Comparison of Baseline and Inverter EPNL, Static Levels. ................... 101 

Comparison of Boardman and 40 by 80 Spectra, Inverter Configuration ........ 102 

Comparison of Boardman and 40 by 80 OASPL and PNL Directivities, 

Inverter Configuration. .............................................. 104 

Comparison of Tunnel-Off and -On Spectra, Inverter Configuration: 

NPR=2.1........................................................ 105 

V 
FIGURES (Continued) 

No. Page 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

61 

62 

63 

Comparison of Tunnel-Off and -On OASPL and PNL.Directivities, 

Inverter Configuration: NPR = 2.1. .................................... 111 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter Configuration: NPR = 2.1. .................................... 114 

Comparison of Tunnel-Off and -On SPL Directivity, Inverter 

Configuration: NPR = 2.1 ........................................... 117 

Velocity Exponents for OASPL and PNL, Inverter Configuration: NPR = 2.1 .... 129 

Velocity Exponents for OASPL and PNL, Inverter Configuration: NPR = 2.1. ... 132 

Velocity Exponents for SPL, Inverter Configuration: NPR = 2.1. ............. 133 

Velocity Exponent versus Frequency, Inverter Configuration: NPR = 2.1 ....... 145 

Comparison of Tunnel-Off and -On Spectra, Inverter Configuration: 

NPR=l.8.....: .................................................. 148 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter Configuration: NPR = 1.8. .................................... 153 

Velocity Exponents for OASPL and PNL, Inverter Configuration: NPR = 1.8. ... 155 

Velocity Exponents for OASPL and PNL, Inverter Configuration: NPR = 1.8. ... 156 

Comparison of Tunnel-Off and -On Spectra, Inverter Configuration: 

NPR=l.6 ........................................................ 157 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter Configuration: NPR = 1.6. .................................... 160 

Velocity Exponents for OASPL and PNL, Inverter Configuration: NPR = 1.6. ... 161 

Velocity Exponents for OASPL and PNL, Inverter Configuration: NPR = 1.6. ... 162 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter Configuration: NPR = 1.4. .................................... 163 

Tunnel-Off and -On OASPL and PNL versus Primary Velocity, 

Inverter Configuration. .............................................. 164 

Static and Estimated Flight EPNL Characteristics, Inverter Configuration ....... 176 

Comparison of Static and Flight OASPL Directivity for Baseline and 

Inverter .......................................................... 177 

Comparison of Static and Flight PNL Directivity for Baseline and Inverter. ...... 178 

Comparison of Baseline and Inverter EPNL, Flight Levels. ................... 179 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, Internal 

Mixer Configuration ................................................ 180 

Velocity Exponents for OASPL and PNL, Internal Mixer Configuration ........ 182 

Static and Estimated Flight EPNL Characteristics, Internal Mixer 

Configuration ..................................................... 184 

Comparison of Static and Flight OASPL Directivity for Baseline, Inverter, 

and Internal Mixer. ................................................. 185 

Comparison of Static and Flight PNL Directivity for Baseline, Inverter, 

and Internal Mixer. ................................................. 186 

Comparison of Baseline, Inverter and Internal Mixer EPNL, Static Levels. ....... 187 

Comparison of Baseline, Inverter and Internal Mixer EPNL, Flight Levels ....... 188 

Comparison of Baseline and Inverter/Plug Spectra ......................... 189 

vi 
FIGURES (Concluded) 

No. Page 

64 

65 

66 

67 

68 

69 

70 

71 

72 

73 

74 

75 

76 

77 

78 

79 

80 

81 

82 

83 

84 

85 

86 

87 

88 

89 

90 

91 

92 

Comparison of Baseline and Inverter/Plug and Inverter Spectra ............... 

Comparison of Static OASPL and PNL Directivity, Baseline versus 

Inverter/Plug and Inverter ............................................ 

Comparison of Tunnel-Off and -On Spectra, Inverter/Plug Configuration. ....... 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter/Plug Configuration. .......................................... 

Velocity Exponents for OASPL and PNL, Inverter/Plug Configuration ......... 

Tunnel-Off and -On OASPL and PNL versus Primary Velocity, 

Inverter/Plug Configuration. .......................................... 

Static and Estimated Flight EPNL Characteristics, Inverter/PIug Configuration ... 

Comparison of Baseline; Inverter/Mixer with and without Shield Spectra. ....... 

Comparison of Static OASPL and PNL Directivity, Baseline versus Inverter/ 

Mixer with and without Shield ........................................ 

Comparison of Tunnel-Off and -On Spectra, Inverter/Mixer Configuration. ...... 

Comparison of Tunnel-Off and -On Spectra, Inverter/Mixer/Shield 

Configuration.. ................................................... 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter/Mixer Configuration ......................................... 

Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter/Mixer/Shield Configuration. ................................... 

Velocity Exponents for OASPL and PNL, Inverter/Mixer Configuraton ......... 

Velocity Exponents for OASPL and PNL, Inverter/Mixer/Shield Configuration. .. 

Tunnel-Off and -On OASPL and PNL versus Primary Velocity, 

Inverter/Mixer Configuration ......................................... 

Tunnel-Off and -On OASPL and PNL versus Primary Velocity, 

Inverter/Mixer/Shield Configuration. ................................... 

Static and Estimated Flight EPNL Characteristics, Inverter/Mixer 

Configuration.. ................................................... 

Static and Estimated Flight EPNL Characteristics, Inverter/Mixer/Shield 

Configuration.. ................................................... 

Comparison of Static and Flight OASPL Directivity for Baseline and 

Inverted Flow Suppressors ........................................... 

Comparison of Static and Flight PNL Directivity for Baseline and 

Inverted Flow Suppressors ........................................... 

Comparison of Baseline and Inverted Flow Suppressor EPNL, Static Levels. ..... 

Comparison of Baseline and Inverted Flow Suppressor EPNL, Flight Levels. ..... 

Comparison of Engine Thrust Coefficients ............................... 

Inverter Exit Flow Survey (Pressure Plot). ............................... 

Inverter Exit Flow Survey (Temperature Plot) ............................ 

Inverter Exit Flow Survey (Velocity Plot). ............................... 

Comparison of Model Static OASPL and PNL Directivity, Baseline, 

Inverter, and Internal Mixer .......................................... 

Model and Full Scale Peak PNL versus Velocity Ratio ...................... 

190 

191 

192 

195 

197 

199 

202 

203 

205 

206 

209 

212 

213 

214 

216 

218 

222 

226 

227 

228 

229 

230 

231 

232 

234 

235 

236 

237 

238 

Vii 
FLIGHT EFFECTS ON NOISE GENERATED BY THE JTSD ENGINE 

WITH INVERTED PRIMARY/FAN FLOW AS MEASURED IN 

THE NASA-AMES 40- BY 80-FOOT WIND TUNNEL 

Frank G. Strout 

Boeing Commercial Airplane Company 

1 .O SUMMARY 

Tests were conducted at the Boeing-Boardman site and the NASA-Ames Research Center 

(ARC) 40- by 80-Foot Wind Tunnel to study the static and flight noise characteristics of 

the JT8D engine with inverted primary and fan flow. The objectives of the program were 

to: 

0 Design and fabricate a primary/fan inverter duct for the JT8D engine 

0 Determine static noise characteristics of the engine with uninverted and inverted flow 

0 Determine flight effects on noise generated by the inverted profile and compare with 

previously obtained results for uninverted and mixed flows 

0 Evaluate static and flight noise suppression potential of the inverted profile with 

several exhaust nozzle modifications 

The test at the Boardman, Oregon site was conducted to establish proper engine match, 

measure thrust performance, and define static far field noise characteristics and near to far 

field correlations. Configurations included the baseline (uninverted flow with conical 

nozzle), the inverter with a conical nozzle and a plug nozzle, and the inverter combined with 

a 20 lobe external mixing nozzle. The 20 lobe configuration was tested with and without 

an acoustically lined shield. Noise data were measured on three sidelines covering a range 

of far field angles from 50’ to 155’ and near field angles from 30’ to 165’. At takeoff 

power and a 649 m sideline the basic inverter (conical nozzle) achieved static peak to peak 

PNL and EPNL suppression values of 5.5 PNdB and 5.0 EPNdB relative to the baseline. 

Suppression values ranged up to 10 EPNdB for the inverter configuration with 20 lobe nozzle 

and acoustic shield. 

The wind tunnel test results showed that significant noise changes occur in going from static 

to flight operation. Relatively large reductions were observed in the peak to peak PNL 

suppression values. The PNL suppression of the basic inverter was reduced from the static 

value of 5.5 PNdB to 2.5 PNdB under flight conditions. The EPNL suppression was not as 

severely influenced by forward velocity, changing from a static value of 5.0 EPNdB to an 

in-Bight value of 4.0 EPNdB. 

The inverter with 20 lobe nozzle and acoustic shield provided the highest in-flight EPNL 

suppression of 7.5 EPNdB. 
The inverted flow profile produces lower noise than the mixed profile under both static and 

flight conditions at takeoff power. The inverter noise is lower by 3 EPNdB during static 

operation and by 1 EPNdB during flight operation. 

The inverter configurations experience thrust loss relative to the baseline. The thrust loss at 

takeoff power ranged from 1.5% for the basic inverter to 5% for the inverter with 20 lobe 

nozzle. 

2 

- 
2.0 INTRODUCTION 

Static model tests conducted by Boeing and others in industry have shown that inverting 

the primary and fan streams of a turbofan engine offers significant potential for reducing jet 

noise. The suppression concept is of particular interest to Advanced Supersonic Transport 

(AST) engine cycle studies where high jet velocities create a serious noise problem during 

takeoff operation. NASA is sponsoring programs to determine the effect of forward 

velocity on the suppression characteristics of model jets with inverted flow. The influence 

of scaling and engine operating characteristics on the effectiveness of the inverted flow concept will remain as a major concern. 

The purpose of this program is to establish the static and flight noise characteristics of a 

JT8D engine with inverted primary and fan flow. The JT8D engine matches important 

AST cycle flow parameters reasonably well and allows a large scale evaluation of the 

inverted flow concept to be made. The static data were acquired at the Boeing test facility 

at Boardman, Oregon while the simulated flight data were measured in the NASA-Ames 

Research Center 40- by 80-Foot Wind Tunnel (40 by 80). The feasibility of using the 40 

by 80 wind tunnel to determine flight effects on engine noise was established by NASAAmes Contract NAS2-8213 (references 1 to 3). The program included model tests with 

near and far field measurements and full scale JT8D engine tests using near field measurements. The model test showed that flight effects measured in the near field are the same 

as those measured in the far field. The JT8D engine test showed that the flight noise 

determined in the wind tunnel matched measured flight noise of the 727/JT8D for a baseline and quiet nacelle installation. 

The inverted flow program consists of the following major elements: 

a Design and fabricate a primary/fan inverter duct for the JT8D engine 

0 Conduct a static, free field test to define far field noise characteristics and establish 

near to far field correlations 

l Conduct a flight effects test in the 40 by 80 

Wind tunnel derived flight effects for the JT8D with inverted flow and a conical nozzle are 

compared with corresponding results previously obtained for the JT8D configured as a baseline and internal mixer. Static and wind tunnel tests were also conducted with Boeing 

supplied nozzle variations to further explore the noise suppression potential of the inverted 

flow concept. The add-on configurations were designed to increase the mixing perimeter 

and mixing rate of the high velocity primary flow. This was done by replacing the conical 

nozzle with a plug nozzle and a 20 lobe nozzle. The effect of an acoustic shield on noise 

was also evaluated. 

3 
3.0 ABBREVIATIONS AND SYMBOLS 

ARC 

AST 

B&K 

CO3 

CV 

C/L 

CONFIG 

dB 

D 

EPNL 

EPNdB 

EPR 

EXTR 

FREQ 

GRD 

kn 

L 

m 

MIC 

n 

ambient 

Ames Research Center 

Advanced Supersonic Transport 

Bruel & Kjaer 

ambient speed of sound, m/s 

engine thrust coefficient 

centerline 

configuration 

decibel 

diameter, m 

effective perceived noise level, EPNdB 

unit of effective perceived noise level 

engine pressure ratio - PT7/PT2 

extrapolated 

one-third octave band center frequency, Hz 

ground 

knot 

length, m 

velocity exponent corrected for source convection 

microphone 

freestream Mach number 

velocity index 

4 
NPR 

OASPL 

OB 

P&WA 

PNdB 

PNL 

P amb 

PT 

‘T2 

‘T7 

‘TF7 

‘TM7 

R 

RC 

RE 

RH 

S/N 

SL 

SPL 

T 

T amb 

TT7 

TTF7 

V 

nozzle pressure ratio - PT7/Pamb 

overall sound pressure level, dB 

octave band 

Pratt & Whitney Aircraft 

unit of perceived noise 

perceived noise level, PNdB 

ambient pressure, N/m2 

total pressure, N/m2 

engine inlet total pressure, N/m2 

exhaust nozzle primary total pressure, N/m2 

exhaust nozzle fan total pressure, N/m” 

exhaust nozzle mixed total pressure, N/m2 

radial distance from sound source to observer, m 

round convergent 

referenced to 

relative humidity, percent 

Strouhal number 

sideline 

sound pressure level, dB 

temperature, OC 

ambient temperature, ‘C 

primary total temperature, OC 

fan total temperature, OC 

velocity, m/s 

5 
I 1111 

Vfan 

V mix 

V Pe 

VR 

V, 

XS 

40 by 80 

A 

A 

e 

OF 

% 

00 

6 

engine fan jet velocity, m/s 

jet velocity of mixed fan and primary flows, m/s 

engine primary jet velocity, m/s 

relative jet velocity = Vpri - V,, m/s 

aircraft or tunnel velocity, m/s 

axial distance from nozzle exit to noise source, m 

NASA-Ames 40- by 80-Foot Wind Tunnel 

delta 

wave length, m 

angle, deg 

far field angle, deg 

noise emission angle, deg 

ambient 
4.0 TEST DESCRIPTION 

4.1 STATIC TEST 

The static test phase of the inverter program was conducted at the Boeing facility located 

at Boardman, Oregon during the period January 4 to 3 1. 1977. 

4.1.1 FACILITY DESCRIPTION 

The facility includes a steel test stand that is attached to a concrete footing. A concrete 

acoustic arena is adjacent to the concrete footing and covers an area of approximately 

5575 sq.m. (60,000 sq. ft.). The test stand and part of the acoustic arena are shown in 

figure I. The test engine is mounted as a 727 center engine at a centerline height of 4 m 

(I 3 ft). The surface between the engine centerline and the near field microphone array was 

covered with a 7.6 cm (3 in.) thick pad of polyurethane foam (figure I). 

4.1.2 ENGINE DESCRIPTION 

The test engine was a JTSD-I 7R turbofan with bypass ratio I. I and a nominal air flow rate 

of 148 kg/set (326 Ib/sec). The engine develops a thrust of 77.9 kn (16,400 lb) at a 

pressure ratio of 2.2. The engine has a two-stage fan, and eleven-stage high pressure compressor, a single-stage high pressure turbine, and a three-stage low pressure turbine. 

4.1.3 TEST HARDWARE DESCRIPTION 

Each configuration was tested with a Pratt&Whitney (P&WA) reference bellmouth inlet 

(engine match and thrust) and a quiet nacelle two-ring inlet (acoustics). All acoustic runs 

included both upper and lower cowling. A schematic drawing of test configurations is 

provided in figure 2. 

4.1.3. I Inverter Duct 

The inverter duct is a series of constant area, nested duct elements that invert the fan and 

primary flow streams of the JTSD engine (figure 3). The welded assembly includes eight 

primary and eight fan gas flow passages and has a length of 0.914 m (3 ft). The flow at the 

inverter exit consists of an outer annulus of high temperature primary gas and an inner 

annulus of fan air. The inverter attaches at the engine “M” flange on the upstream end and 

mates with a modified production tailpipe on the downstream end. Some mixing occurs 

between the two streams prior to exhausting through a conical nozzle. 

4. I .3.2 Baseline 

The baseline configuration operated with conventional or uninverted flow with the high 

velocity primary on the inside and the low velocity fan flow on the outside. The two 

streams merge downstream of the fan splitter case and exhaust through a 0.76 m (2.5 ft) 

diameter production conical nozzle. 

7 
4.1.3.3 Inverter 

The primary/fan inserter contigurarion was operated with the inverter duct installed downstream of the splitter case. 1 he inverter duct is followed by a modified production tailpipe 

and a conical exhaust nozzle. The high velocity primary is located in an outer, annular flow 

region with the fan air located on the inside. The nozzle diameter is about the silme as the 

baseline although slightly larger to compensate for the inverter duct pressure loss. At takeoff 

power the primary to fan area ratio is I .4 and the velocity ratio is I .6. 

4.1.3.4 Inverter/Plug 

This configuration included the inverter duct but replaced the conical nozzle with a conical 

plug nozzle. The plug has a maximum diameter of 0.54 m (1.76 ft) providing a total to flow 

area ratio of ) .5. 

4. I .3.5 Inverter/Mixer 

This contigoration replaces the conical nozzle of the inverter/plug with a 20 lobe external 

mixing nozzle. The lobes are designed to penetrate the outer primary flow (about 12.1 cm) 

and rapidly mix this flow with ambient air. Each lobe has a length of 35.4 cm (IO in.). 

4.1.3.6 Itlverter/Mixer/Shield 

An acoustic shield is added to the inverter/mixer to provide a reflecting/absorbing barrier 

between the jet and observer. The shield has a length and diameter of 1.27 m (4.2 ft) covering a 180’ segment. The inner shield surface includes bulk absorber acoustic lining covered 

by a perforated plate. The shield was tested in a hardwall and lined configuration. The 

shield was designed to retlect and absorb the high frequency pre-merged mixing noise 

generated by the 20 lobe nozzle. 

4. I .4 INSTRUhiENTATlON 

4.1.4.1 Engine Instrumentation 

In addition to thrust. rotor speed. and fuel flow. normal engine gas flow pressures and 

temperatures were measured. Engine air flow was measured during perfomvmce runs by 

means ofa calibrated bellmouth inlet. A survey of the inverter exhaust flow was made with 

a rake having 40 total pressure and 40 total temperature probes. A 180’ segment was 

covered by the survey. 

4.1.4.2 Acoustic Instrumentation 

The acoustic instrumentation (table I) included three microphone arrays located on sidelines of 3.0.5 m (I 0 ft), 15.2 m (SO ft), and 30.5 m (I 00 ft). The mar array employed 

I6 centerline microphones covering a range of angles from 30’ to 165’ referenced to the 

nozzle exit plane and inlet axis. The intermediate array used I5 ground microphones 

covering angles from 30° to 160’. The far array were also ground microphones and included I3 microphones from 50’ to I55O. The near array used 0.64 cm (0.25 in.) Bruel & 
Kjaer (B&K) 4136 microphones that were oriented for grazing incidence (figure I). The 

other two arrays used I .21 cm (0.5 in.) B&K 4134 microphones that were oriented downward, I .27 cm (0.5 in.) above individual steel plates. 

Noise data were recorded on a fourteen track Sangamo model 3500 tape recorder. On-line 

data were processed by a General Radio 1925 filter, 1926 detector, and a Hewlett Packard 

700 IA plotter. 

4.1.5 ACOUSTIC DATA REDUCTlON 

Data reduction provided one-third octave band (OB) spectra in the form of a digital 

magnetic tape. 

4.1.6 TEST PROCEDURE 

Each configuration included an engine match run, a thrust performance run. and an acoustic 

run. The match run. was made to &sure that the engine was operating within limits 

prescribed by P&WA for a flight-worthy engine. The inverter duct included tabs to adjust 

the relative fan and primary flow areas. The nozzle exit area was also adjusted to assure 

proper engine operation with the inverter test hardware. The engine match and thrust 

performance runs were conducted with the bellmouth inlet. Following engine start and a 

nominal five minute warm-up. the test conditions were set starting with the lowest pressure 

ratio. After a three minute stabilization time at each pressure ratio, engine performance 

data were recorded. During acoustic runs, noise data recording began as soon as the target 

condition was established. Engine performance was calculated onsite immediately after 

each test condition to assure that the desired condition was set. 

4.1 .I TEST CONDITIONS 

Engine test conditions for the acoustic runs are listed in table I. Match and thrust performance runs generally covered a range of pressure ratios from I .4 to 2.2. 

4.2 WIND TUNNEL TEST 

The wind tunnel test phase of the inverter program was conducted at the NASA-Ames 

Research Center 40. by SO-Foot Wind Tunnel (40 by 80) during the period June I3 to 

24, 1977. 

4.2.1 FACILITY DESCRIPTION 

The 40 by 80 is a closed circuit wind tunnel powered by six 12.2 m diameter fans and six 

4480 kw electric motors. The test section is 24.4 m long in the tunnel airflow direction and 

has a cross section consisting of a 12.2 m square and two semicircles of 12.2 m diameter on 

each side of the square section (figure 4). The tunnel operates with a stagnation pressure 

equal to the atmospheric pressure. The tunnel stagnation temperature is time variant 

because of the wind tunnel drive power and engine exhaust. Typically the temperature 

would range between 15% to 55oC (60’F to 130’F). About 400 sq. m of 7.6 cm-thick 

9 
polyurethane foam was installed on the floor and part way up the sidewalls. The lining 

extended approximately 3 m upstream of the engine exit plane and 15 m downstream. The 

test installation is shown in figures 4 and 5. 

4.2.2 TEST CONFIGURATIONS 

The following configurations were tested in the 40 by 80: 

@ lnverter (figure 4) 

a Inverter/plug (figure 5) 

a Inverter/rnixer (figure 6) 

0 Inverter/mixar/lined shield (tigurr 7) 

Each configuration included the quiet nacelle two-ring inlet and full engine cowling. Additional configuration description is provided in section 4. I .3. The JTIID-I 7 engine configured 3s a baseline and with an internal mixer were tested in the 40 by 80 during Contract 

NASI-82 I3 (references I and 3). 

42.3 INSTRUhlENTATION 

4.2.3.1 Engine Instrumentation 

Engine operating parameters were measured including rotor speeds, fan and primary static. 

and total pressures and temperatures. 

4.2.3.2 Acoustic Instrumentation 

Acoustic data for flight effects analysis were recorded by a pair of traversing microphones 

in swrp mode (tigures 4 and 5). The microphones were 0.64 cm (0.25 in.1 B&K type 

4136 with B&K UA 0385 aerodynamic nose cones. They were mounted at engine centerline height (4 m) on a 3.05 m sideline relative to the center of the jet. The traverse moved 

at a steady rate of 0. I5 m/w (0.5 ft/sec) and covered a range of angles from 30” to 168” 

relative to the nozzle exit plane and inlet axis. In addition to the traverse microphones. two 

fixed microphones were installed on the side opposite the traverse. One fixed microphone 

was mounted at centerline height on a 3.05 m sideline at 160” for on-line monitoring. 

The second fixed microphone was positioned on the same sideline but at a height of I .8 m 

and an angle of 8”. These data were recorded and used as an indication of the reverberant 

field noise level. The noise data were recorded on a fourteen track Sangamo model 3500 

type recorder for later reduction at Boeing. 

4.2.3.3 Facility Instrumentation 

Tunnel parameters were recorded on the Boeing data system including static and total 

pressure. total temperature, and relative humidity. It is noted that engine thrust was not 

measured. 

IO 
4.2.4 ACOUSTIC DATA REDUCTION 

The sweep data were analyzed to define one-third octave band spectra each 5O from 30’ 

through 110’ and every 2.5’ from 112.5O through 167.5O. A one second integration time 

was used, 0.5 second before and after the desired angle. 

4.2.5 TEST PROCEDURE 

Engine test conditions were set by monitoring nozzle pressure ratio (PT7/Pamb) and on-line 

calculated primary jet velocity. At the start of each run, the desired primary jet velocity 

was set and maintained as closely as possible until all data were recorded. The traverse 

microphones were positioned in the region of peak noise where gains were set and on-line 

data were recorded. The traverse was then moved to a position just downstream of 30’. 

A sweep was then made to an angle of 168’ with each microphone output recorded on two 

channels at different gain settings. One channel recorded the microphone position voltage 

output and another the voice input. Two propulsion data points were recorded during each 

traverse, one near the beginning and the other near the end. 

Selection of engine power setting.and tunnel velocity was made on the basis of tunnel 

heating. Periods with the engine at idle power and test section ventilation doors open were 

used on occasion to reduce tunnel temperature prior to another run. 

4.2.6 TEST CONDITIONS 

Engine and wind tunnel test conditions are listed in table 2 for each configuration. 

11 
5.0 DATA ANALYSIS 

5.1 ANALYSIS TECHNIQUE 

5.1 .l NOISE SOURCE LOCATIONS 

The technique for determining flight effects in a closed wind tunnel requires that noise 

source locations and directivities be known for the frequencies of interest. The multiple 

sideline noise measurement procedure described in references 1 to 3 is used to define the 

required source location correlations. Sound pressure level (SPL) directivities were plotted 

as a function of 1 /tan (180’ - 0) for the three sideline microphone arrays and each one-third 

octave band from 50 to 10,000 Hz. Typical plots for the inverter configuration are shown in 

figure 8 for takeoff power and a range of frequencies. The difference in peak noise levels 

is used as a basis for relating a given signal that propagates from the source through the 

three sidelines. This peak to peak difference includes the effect of spherical divergence, 

atmospheric absorption, and noise measurement in the near field. For high frequencies the 

peak to peak increment is adjusted to account for longer or shorter propagation paths 

relative to the peak noise. The adjustment is determined by multiplying the difference in 

propagation length by the atmospheric absorption coefficient. The procedure is illustrated 

in figure 8a for frequencies of 200 and 250 Hz. The peak to peak SPL increments for 

200 Hz are about 14 dB between the 30.5 and 3.05 m sidelines and 6 dB between the 30.5 

and 15.2 m sidelines. Since atmospheric attenuation is very small for this frequency range, 

the 14 dB and 6 dB increments are used to track a given signal from each 30.5 m microphone station to a corresponding station on the other sidelines. For each measured SPL on 

the 30.5 m sideline, increments of 6 dB and 14 dB are added and define intercepts on the 

15.2 m and 3.05 m sidelines respectively. The intercepts on each sideline are joined by the 

dashed lines of figure 8a that establish propagation paths for each signal. 

The intercept of the dashed lines with each sideline defines an axial station equal to the 

sideline distance times (l/tan (180’ - 0). These results are plotted as shown in figure 9. 

A line drawn from the 30.5 m measurement position through the corresponding points 

from the other two sidelines defines the apparent source location and directivity for a given 

signal. The source locations of figure 9 show that noise propagating to low angles appears 

to emanate from a point near the nozzle exit. The source location moves downstream as 

the propagation angle increases. 

The source location and directivity from figure 9 is replotted as shown in figure 10. The 

source location, in terms of nozzle diameters, is defined as a function of noise emission 

angle for takeoff power and the available range of Strouhal numbers. Source location results 

for nozzle pressure ratios of 1.4 to 2.2 were used to define the correlation curves of figure 

11. These relationships covered a wide range of Strouhal numbers and served as inputs to 

a computer program that extrapolated data from the three sidelines to a 122 m (400 ft) 

sideline. The 122 m data were treated as far field, thus permitting point source extrapolations to other sidelines. 

The near field level effect described in reference 3 is also observed for the full scale data. 

The correlation shown in figure 12 was used as an input to the data extrapolation program 

to compensate for this effect. For the 3.05 m data (SL/D = 4) the near field effect is up to 

2 dB. The 15.2 m and 30.5 m data require no level adjustment for near field effects. 

12 
The source location and near field level correlations of figures 11 and 12 were used to 

extrapolate the Boardman static data and the 40 by 80 wind tunnel data for the inverter 

configuration. Similar correlations were defined for each of the other configurations that 

are evaluated in this report. 

5.1.2 WIND TUNNEL REVERBERANT FIELD 

Although part of the test section hard surface was covered by polyurethane foam, a prominent reverberant field problem remains. The reverberant field is found to be a function of 

frequency, engine power condition, nozzle configuration, and tunnel velocity. The 

reverberant level at a given frequency appears to be strongly related to the peak level that is 

generated. Thus the reverberant field becomes a problem at off-peak angles (low and high) 

and is more pronounced when there is a large fall-off in SPL at off-peak angles, Since the 

reverberant field is related to the peak SPL values, it will vary with the engine power condition and tunnel velocity. The nozzle configuration will influence the peak noise generated 

at each frequency and the directivity characteristics. 

Reverberant field spectra were defined for each engine configuration, engine power condition, and wind tunnel operating velocity. The spectra for the inverter configuration are 

shown in figure 13 and represent nominal reverberant field noise levels within the test 

section for the specified test condition. The 40 by 80 noise data were corrected by logarithmically subtracting the reverberant field spectra from the measured engine noise 

spectra at each angle. 

Different techniques were used to determine the reverberant field noise level for tunnel-off 

and -on operation. The tunnel-off reverberant field was determined by logarithmically 

subtracting free field SPL’s from the 40 by 80 SPL values at equal primary jet velocity. 

This procedure is illustrated in figure 14 for takeoff power and several frequencies. The 

reverberant field noise level at a given frequency appears to be relatively constant through 

the test section. A nominal reverberant field level is estimated for each frequency and 

tunnel-off power condition to form the spectra shown in figure 13a. 

A different procedure is required to estimate the reverberant field for tunnel-on operation. As indicated in figure I3a, the tunnel-off reverberant field level is quite sensitive to 

engine power condition. It is reasonable that as the engine power is reduced the reverberant 

field level will be lower due primarily to reduced noise source strengths at each frequency. 

Tunnel velocity should have an effect similar to engine power reduction since source 

strengths are reduced as tunnel velocity increases. Two methods were combined to estimate 

the reverberant field level during tunnel-on conditions. One method employed a correlation 

between peak SPL and reverberant field level while the other method relied on 8O microphone spectra measured in the 40 by 80 test section. 

The peak SPL correlation is shown in figure 15 and is based on the tunnel-off reverberant 

field data. Each data point represents the difference between the peak SPL measured on 

the 3.05 m sideline and the resulting reverberant field level for a given engine power condition and frequency. Data are included for NPR’s of 1.1 to 2.1 and show that the reverberant field level is closely related to the peak.SPL that is generated. The directivity of the 

peak SPL undoubtedly influences the resulting reverberant field level. That is, spherical 

13 
divergence noise reduction beyond the 3.05 m sideline will be less at 90’ than in an upstream or downstream direction. The solid symbols of figure 15 reflect a spherical divergence level adjustment due to changes in peak noise directivity. The adjustment is made 

relative to directivity characteristics of the NPR = 2.1 condition. The data for NPR 2.1 and 

the adjusted data for lower power conditions collapse reasonably well. The purpose of this 

correlation is to show that the change in reverberant field level will follow the change in 

measured peak SPL. Although the difference in peak SPL between NPR 2.1 and NPR 1.1 

is quite large for all frequencies (about 20 dB), the resulting reverberant levels are predictable within approximately 1 dB based on figure 15. This finding is used to determine 

the tunnel-on reverberant field level by incrementing from the tunnel-off level. The increment is determined for each frequency by the change in peak SPL between tunnel-off and 

tunnel-on operation at a given power condition. Adjustment for changes in peak noise 

directivity is made, if required. 

The second method for estimating the tunnel-on reverberant field level used spectra measured by a microphone located in the forward part of the test section. The microphone was 

positioned opposite the traverse on a 3.05 m sideline at an angle of 8’ referenced to the 

nozzle exit station and the inlet axis. It was surmised that the measured signal might be 

representative of the test section reverberant field level due to the low engine noise radiated 

to this position. Typical 8’ microphone spectra are provided in figure 16 for takeoff power 

and both tunnel-off and tunnel-on operation. It is noted that the tunnel-on spectra have 

been corrected for tunnel background noise. Tunnel-off reverberant field levels determined 

by the method of figure 14 are plotted for comparison with the tunnel-off 8’ microphone 

spectra. The agreement is good as it was for lower power conditions and the other configurations. 

This analysis shows that the 8O microphone spectra provides a good estimate of reverberant 

field level for tunnel-off conditions. When corrected for background noise, the 8’ microphone spectra should also provide a reasonable estimate for tunnel-on operation. The 

tunnel-on 8’ microphone spectra of figure 16 is lower than the tunnel-off spectra which is 

expected. A check on the level is made by applying the change-in-peak-SPL method that 

was previously described. The incremental reductions in peak SPL between tunnel-off 

and tunnel-on are equated to corresponding reductions in reverberant field level. The 

increments are subtracted from the tunnel-off reverberant field level and define an estimated 

tunnel-on reverberant field level as shown in figure 16. The resulting spectra compare 

favorably with the measured 8’ microphone spectra for tunnel-on operation. Thus both 

methods appear to provide about the same estimate for the tunnel-on spectra of figure 13. 

The spectra are based primarily on the measured 8O microphone spectra. Level checks and 

adjustments were made by the peak SPL increment method. For cases where tunnel background noise obscured the 8’ microphone data, the SPL increment technique was used 

exclusively. 

5.1.3 BACKGROUND NOISE 

Wind tunnel background noise levels were subtracted from the tunnel-on data. Background 

noise was measured during the inverter test and the inverter/mixer test with and without 

shield. No significant difference was noted due to configuration; thus the background noise 

taken during the inverter test was used for all configurations. A background noise spectra 

was defined for each angle of interest between 30’ and 165’ as typified by figure 17. 

14 
5.2 BASELINE ANALYSIS 

Data for the JT8D-17R engine configured as a baseline (uninverted flow) was acquired during 

the Boardman test phase. Wind tunnel data were measured during contract NAS218213 

(references 1 and 2) using a JT8D-17 engine. The -17 and -17R engines generate near 

identical static jet noise; consequently, the flight effects measured for the -17 are assumed 

to be applicable to the -17R. 

5.2.1 STATIC DATA ANALYSIS 

The measured 30.5 m (100 ft) sideline data were extrapolated to the far field using source 

location correlations described in reference 1. The resulting spectra, OASPL and PNL 

directivities, and EPNL characteristics are compared with corresponding data for the suppressor configurations in following sections. In general, spectra comparisons are made on a 

122 m (400 ft) sideline that is considered to be far field. Directivity and EPNL comparisons 

emphasize a 649 m (2 128 ft) sideline (AST noise certification sideline). Some comparisons 

are also provided for an intermediate sideline of 457 m (1500 ft) to establish trends as a 

function of sideline distance. 

5.2.2 WIND TUNNEL DATA ANALYSIS 

The wind tunnel data from the previous test were re-processed using the technique described 

in section 5.0. The resulting tunnel-off and tunnel-on OASPL and PNL directivities are 

compared in figure 18 for NPR 2.1 and 1.8. The results of figure 18 are converted to velocity coefficients (n) in figure 19 where: 

OASPLstatic - OASPLflight 

n= 

v . 

lOlog 

vR 

Effective perceived noise level (EPNL) is used to evaluate the noise reduction effectiveness 

of the various suppressor configurations in this report. EPNL is the logarithmic summation 

of PNL each 0.5 second between the 10 PNdB down points from the peak PNL. The calculation for both static and flight EPNL assumes a single engine moving past an observer at a 

velocity of 91.5 m/s (300 ft/sec) and at a distance of 649 m (2128 ft). Installation on an 

aircraft, angle of attack, flight trajectory, ground reflections, and extra ground attenuation 

are factors that are not included in the calculation. 

A static and flight EPNL comparison is provided in figure 20 for the baseline configuration. 

The static or solid line is plotted as a function of primary velocity and defines a throttle 

line for comparison with flight EPNL. The EPNL values are calculated using far field static 

PNL data assuming no change in level due to forward velocity. The diamond symbols 

represent flight EPNL’s and are plotted versus primary relative velocity. 

15 
The flight levels are calculated by applying PNL velocity exponents (figure 19) to the static 

PNL values where: 

v . 

PNLEght = PNLstatic - 1 On log 2 

VR 

The comparison of figure 20 shows that the EPNL reduction due to flight is less than 

predicted by relative velocity. That is, the diamond symbols would fall on the solid throttle 

line if the relative velocity prediction were correct. The departure from the throttle line is 

less at high power than at low power. 

5.3 INVERTER ANALYSIS 

The analysis of the inverter configuration data is given major emphasis in this report. Analysis of the other configurations was done in a similar manner but is not reported in as much 

depth. 

5.3.1 STATIC DATA ANALYSIS 

5.3.1 .l Comparison of Near and Far Field Data 

Comparisons are made between static noise data measured on the three sidelines and extrapolated to the same far field sideline using source location correlations. Spectra are compared in figure 2 1 for the 3.05 and 30.5 m data at a NPR of 2.1. The spectra compare 

reasonably well in terms of shape and absolute level. OASPL and PNL directivities are 

compared in figure 22 for the noted pressure ratios. Agreement between the three sidelines 

is generally good in terms of level and directivity shape. 

Another method of comparing near and far field data is illustrated by figures 23 and 24 that 

plot OASPL and PNL as a function of ideal primary velocity. The slope and level of OASPL 

and PNL compare well between the extrapolated 3.05 and 30.5 m data. These comparisons 

along with the spectra and directivity plots indicate that the noise source location correlations of figure 11 are satisfactory. Near and far field comparisons were also made at lower 

power conditions with similar favorable results. 

Good agreement between near and far field results is quite important to the analysis of the 

wind tunnel data. These measurements are restricted to the 3.05 m sideline and must be 

extrapolated to define far field flight effects. Verification of the source location correlations provides confidence that the resulting flight effects for the inverter will be relatively 

accurate. 

5.3.1.2 Comparison of Inverter and Baseline Data 

Static data for the inverter configuration are compared with data for the baseline configuration in this section. In all cases the data were measured on the 30.5 m sideline and extrapolated to the far field using source location correlations. Spectra comparisons are provided 

in figures 25 to 29 for NPR’s of 2.2, 2.1, 1.8, 1.6, and 1.4. Emphasis is placed on the NPR 

16 
2.1 condition since this represents the highest power tested for flight effects in the 40 by 80. 

At low angles (figure 26) the inverter is not effective in reducing noise, relative to the baseline, regardless of frequency. As the angle increases toward the jet axis the inverter shows 

increasing reduction in the low and middle frequency range. At angles of 130’ to 155’ 

(figures 26e and 26f) the amount of reduction is quite substantial in particular for frequencies in the region of 200 to 400 Hz (6 to 10 dB). At high frequencies (above 1600 Hz) 

the baseline and inverter have comparable noise levels. Similar results are observed for the 

other power conditions. 

Baseline and inverter static OASPL and PNL directivities are compared in figure 30 for 

NPR’s of 2.2 to 1.4. In general, the inverter is an effective suppressor at angles of 120’ 

and higher. At takeoff power (NPR 2.2) peak to peak suppression for OASPL is 6.0 dB and 

for PNL is 5.5 PNdB. The low angle (50’ to 110’) suppression of OASPL and PNL is 

relatively small. 

Static EPNL characteristics are compared in figure 3 1, where flight PNL’s are assumed to 

equal static values. At takeoff power (600 m/s) the inverter provides an EPNL suppression 

of 5.0 EPNdB. The amount of EPNL suppression is reduced slightly as the engine power 

is reduced. 

5.3.2 WIND TUNNEL DATA ANALYSIS 

5.3.2.1 Comparison of Free Field and Tunnel-Off Data 

Boardman free field data are compared with 40 by 80 tunnel-off data in this section. The 

data are measured on a 3.05 m (10 ft) sideline and extrapolated to a 122 m (400 ft) sideline 

using source location correlations. Low angle and high angle spectra are compared in 

figure 32 for a NPR of 2.1. The two sets of data compare reasonably well indicating the 

validity of the reverberant field corrections. It is noted that spikes were observed in the 

40 by 80 spectra at frequencies up to 200 Hz and low angles after correcting for the reverberant field. These spikes were smoothed to fair in with the adjacent frequencies to minimize errors in calculated OASPL and PNL. 

OASPL and PNL directivities are compared in figure 33 for the NPR 2.1 condition. The 

agreement is basically acceptable for both OASPL and PNL. An exact agreement is not 

expected due to the entrained velocity that results during tunnel-off operation. The comparison is made by interpolating the free field data at the wind tunnel primary relative 

velocity. A comparison at equal primary velocity would result in a better match at low 

angles where the-effect of forward velocity is generally small. Comparisons of spectra and 

directivities at lower power conditions also show good agreement between free field and 

wind tunnel. 

5.3.2.2 Flight Effects for NPR 2.1 

Flight effects on engine noise for the inverter configuration at NPR 2.1 are evaulated in 

this section. The analysis includes spectra, OASPL and PNL directivity, and SPL directivity. 

Velocity exponents are defined for OASPL, PNL, and SPL. 

17 
5.3.2.2.1 Spectra 

Tunnel-off and tunnel-on spectra are compared in figure 34 for NPR 2.1 and angles of 

50° to 155O. The sideline is at 122 m (400 ft) and the angles are representative of far 

field. The results show that tunnel velocity produces negligible noise reduction at low 

angles (50° to 100°, figures 34a to 34~). The low frequencies (50 to 3 15 Hz) indicate a 

slight reduction (about 1 dB). The intermediate to high frequencies show either no reduction or a slight increase in noise level with forward velocity. As the angle increases from 

11 O” to 1 50° the amount of SPL reduction with forward velocity increases at all frequencies. At 140’ to 155’ the reduction of the peak noise (125 Hz) is greater than higher or 

lower frequencies. 

5.3.2.2.2 OASPL and PNL Directivity 

Tunnel-off and tunnel-on OASPL and PNL directivities are compared in figures 35 and 36 

for NPR 2.1. The sideline varies from 122 to 649 m for tunnel velocities of 150 and 185 kn. 

Tunnel velocity results in relatively small reductions in OASPL and PNL at angles of 50’ 

to 100’. As the angleincreases, the amount of reduction increases. For the 185 kn tunnel 

condition and a 649 m sideline (figure 36~) a reduction of 5 dB or 5 PNdB results at an 

angle of 140’. The corresponding reductions on the 122 m sideline are slightly less (4.6 

dB and 4.0 PNdB). This difference is the result of atmospheric attenuation that changes 

the spectra shape and weighting of frequencies. 

5.3.2.2.3 SPL Directivity 

Tunnel-off and tunnel-on SPL directivities are compared in figure 37 for NPR 2.1 and 

one-third octave band frequencies from 50 Hz to 10,000 Hz. The data reflect a sideline of 

122 m and tunnel velocities of 150 and 185 kn. In general, tunnel velocity causes a small 

reduction in SPL at low angles (50’ to 100’). Large reductions (6 to 7 dB) are experienced 

at higher angles for frequencies of 100 Hz to 250 (figures 37b to 37d). The reduction of 

high frequency SPL with tunnel velocity is more modest at high angles ranging from 1 dB 

to 3 dB depending upon frequency. 

5.3.2.2.4 Velocity Exponents 

The results of figures 35 to 37 are converted to velocity exponents for OASPL, PNL, and 

SPL in figures 38 to 40. Velocity exponents (n) are provided for OASPL and PNL at 

sidelines of 122,457, and 649 m in figure 38. An alternate velocity exponent (m) is shown 

in figure 39 for a 649 m sideline where the source convection correction is made as follows: 

PNLstatic - PNLflight log( 1 -M, COS 0) 

m=- - 

‘pri v . 

10 logVR 

log -E 

VR 

The velocity exponent curves for OASPL and PNL are consistent with small flight noise 

reductions at low angles and large reductions at angles near the jet axis. The effect of sideline is most prominent for PNL at high angles where higher n values result at the further 

sidelines. 

18 
The velocity exponent curves for discrete frequencies (figure 40) were arrived at by plotting 

the n values as a function of frequency (figure 41). This was done to minimize the effects 

of data scatter and assumes that reasonably smooth variations in n will occur with frequency 

at a given angle. The n curves of figure 40 are defined by the faired data from plots similar 

to figure 41. 

5.3.2.3 Flight Effects for NPR 1.8 

Tunnel-off and tunnel-on data are compared for an NPR of 1.8 in figures 42 to 45. Spectra 

comparisons are provided in figure 42 for a 122 m sideline and angles of 50° to 155’. The 

effects of tunnel velocity on the tunnel-off spectra are comparable with the NPR 2.1 condition described in section 5.3.2.2.1. 

OASPL and PNL directivity plots are shown for 100 and 150 kn tunnel speeds in figure 43. 

Tunnel velocity causes a small reduction in OASPL and PNL at low angles (50’ to 100°) 

with increasing reduction at higher angles. Velocity exponents are provided in figures 44 

and 45 for a 649 m sideline and are similar to the NPR 2.1 curves in terms of trend with 

angle. 

5.3.2.4 Flight Effects for NPR 1.6 and NPR 1.4 

Tunnel-off and tunnel-on spectra are provided in figure 46 for an NPR of 1.6 and a 122 m 

sideline. OASPL and PNL directivities are compared in figure 47 and are used to define the 

velocity exponent curves of figures 48 and 49. The peak velocity exponent values at this 

power condition are significantly less than those at the higher power conditions (figures 

38~ and 44). 

Tunnel-off and tunnel-on OASPL and PNL directivities are compared in figure 50 for an 

NPR of 1.4 and a 649 m sideline. Only the directivity plot is shown for this power condition due to the small difference in test relative velocity between the tunnel-off and -on 

cases. The noise reduction trend with angle is comparable to the higher power conditions. 

Velocity exponents are not calculated because of the small difference in relative velocity 

and the sensitivity of n values to this parameter. 

5.3.2.5 Summary and Comparison of Flight Effects 

Flight effects for the inverter configuration are summarized in this section by evaluating 

trends with relative velocity and by comparison of static and flight OASPL, PNL, and 

EPNL suppression relative to the baseline. Tunnel-off and tunnel-on OASPL and PNL are 

plotted as a function of primary relative jet velocity in figure 5 1. The results are for a 

649 m sideline and cover a range of angles from 50’ to 155’. Static data from the Boardman test are included and are used to define the throttle lines shown on each plot. The 

departure of the tunnel-on data from the static throttle line is quite pronounced at low 

angles (50° to loo’, figures 5 la to 5 If). The use of relative velocity to predict flight noise 

would result in large errors for this range of angles (low predicted noise level). At 1 loo 

and 120’ (figures 5 lg and 5 1 h) the tunnel-on data approaches the throttle line. At angles 

of 130’ and higher the tunnel-on data fall on the throttle line or show the same slope with 

relative velocity. 

19 
Based on these characteristics one approach to estimating the flight noise of inverted profiles for other engines or cycle conditions is as follows: Flight OASPL or PNL can be 

defined by assuming a relative velocity relationship at angles of 120’ and higher. That is, 

interpolate static data or calculate noise levels at a primary velocity equal to flight relative 

velocity (Vpri - V-lane)* Th e reduction of OASPL and PNL at lower angles will best 

be estimated by using the velocity exponents provided in this report. The reduction of 

low angle noise is small regardless of power setting for the JT8D and appears to be a characteristic of the inverted flow profile. Any error in true flight PNL reductions at low angle 

will generally have a small effect on the flight EPNL estimate. 

Static and flight EPNL’s are plotted as a function of primary relative velocity in figure 52. 

The static EPNL values are based on Boardman static PNL’s assuming no reduction in level 

due to flight. The flight EPNL values are calculated by applying the velocity exponent 

curves of figures 38c, 44, and 48 to the static PNL’s. The flight EPNL’s are higher than 

predicted by relative velocity. The departure from the throttle line increases as the engine 

power is decreased. 

Static and flight OASPL and PNL comparisons are provided in figures 53 and 54 for the 

baseline and inverter configurations at takeoff power. The static curves are based on Boardman 30.5 m data that are extrapolated to the 649 m sideline using source location correlations. The flight noise levels are obtained by applying the velocity exponent curves (figures 

19a and 38~) to the static OASPL and PNL values. The peak OASPL suppression is reduced 

slightly in going from static to flight operation (from 6 dB to 5.5 dB). The in-flight OASPL 

suppression is less at low angles and greater at angles of 1 40° and higher. The peak PNL 

suppression is reduced significantly by flight going from 5.5 PNdB to 2.5 PNdB. This is 

due to the inverter having a peak static PNL at 120’ in contrast to 135’ for the baseline 

(figure 54). The reduction of PNL with forward velocity is much smaller for the inverter 

at 120’ than the baseline at 135’ and results in a substantial loss of peak PNL suppression. 

Generally suppressor nozzles have peak PNL values in the 11 O” to 120’ region that are 

dominated by relatively high frequencies. The high frequencies originate close to the nozzle 

exit and experience small level reductions with forward velocity. In contrast, the peak PNL 

of the baseline is dominated by low frequencies having source locations further downstream. 

The low frequencies are substantially reduced by forward velocity providing a corresponding 

large reduction in PNL for the baseline. The in-flight PNL suppression is essentially zero 

at low angles but is greater than the static value at angles of 140’ and higher. Basically 

the inverter is an effective suppressor of OASPL at angles of 120’ and higher and PNL at 

125’ and higher. 

The in-flight EPNL characteristics of the inverter and baseline are compared in figure 55. 

At takeoff power (600 m/s) the suppression is 4.0 EPNdB. This compares with a static 

data estimate of 5.0 EPNdB (figure 3 1) indicating a suppression loss of 1 .O EPNdB due to 

flight. The loss of EPNL suppression is due to the poor in-flight PNL suppression characteristics at low angles (figure 54). 

5.4 INTERNAL MIXER ANALYSIS 

Static and wind tunnel data for the 12 lobe internal mixer were measured using a JT8D-17 

engine as reported in references 1 and 2. 

20 
5.4.1 STATIC DATA ANALYSIS 

Static data were measured on a 30.5 m (100 ft) sideline and extrapolated to the far field 

using source location correlations reported in reference 1. Comparisons of OASPL, PNL, 

and EPNL are made with the baseline and inverter in the following section. 

5.4.2 WIND TUNNEL DATA ANALYSIS 

The wind tunnel data from the previous test were reprocessed using the technique described in section 5.1. Tunnel-off and tunnel-on OASPL and PNL directivities are shown 

in figure 56 for NPR 2.1 and 1.8. From these results the velocity exponent curves of 

figure 57 are determined. 

Static and flight EPNL’s are plotted versus primary relative velocity in figure 58. The 

procedure for calculation of the EPNL values was previously described in section 5.2.2. 

The in-flight EPNL values fall slightly above the throttle line similar to the baseline (figure 20). It is noted that the slope of the throttle line for the internal mixer is steeper than 

that of the baseline. Thus equal departure from the throttle line in terms of EPNL would 

show up as a gain in flight suppression for the internal mixer. 

Static and flight OASPL and PNL directivities for the baseline, inverter, and internal mixer 

are compared in figures 59 and 60. The curves were defined in the manner described in 

section 5.3.2.5. The three configurations represent extremes in jet flow profile. The profile ranges from: the low velocity outer fan and high velocity inner primary flows (baseline); relatively well mixed fan and primary flows (internal mixer); to the high velocity outer 

primary and low velocity inner fan flows (inverter). The comparison of static OASPL shows 

that the inverter and internal mixer produce equal suppression at low angles (50° to 110’) 

but the inverter is significantly better at higher angles. The peak OASPL suppression for 

the inverter is about 6.0 dB while the internal mixer shows about 2 dB. In flight the internal mixer provides about 1 dB lower noise at low angles while the inverter noise is 

significantly lower at high angles. The in-flight peak OASPL suppression of the internal 

mixer improves relative to static operation, going from about 2 dB to 3 dB. The inverter 

experiences a slight loss of peak OASPL suppression due to flight, going from 6.0 dB to 

5.5 dB. 

The effect of flight on PNL suppression characteristics is more pronounced than observed 

for OASPL. Under static conditions (figure 60) the inverter and internal mixer show 

equal suppression at low angles but the inverter suppression at high angles is clearly superior. 

The peak PNL suppression of the internal mixer is about 2 PNdB as opposed to 5.5 PNdB 

for the inverter. 

Under flight conditions the peak PNL suppression of the two configurations is approximately the same (2.5 PNdB). The internal mixer shows a slight gain in peak PNL suppression with forward velocity while the inverter undergoes a significant loss. The primary 

cause of peak PNL suppression loss for the inverter is the low static peak noise angle (120’) 

and relatively small flight PNL reduction at this angle (see section 5.3.2.5). The internal 

mixer provides more PNL suppression at low angles; however, the inverter is the better 

suppressor of PNL at high angles. 

21 
Static and flight EPNL characteristics for the three configurations are compared in figures 

6 1 and 62, At takeoff power (600 m/s) and with static PNL values, the EPNL suppressions 

are 2 EPNdB for the internal mixer and 5 EPNdB for the inverter. At lower power conditions the difference in suppression becomes smaller. It is noted that the internal mixer 

has less thrust loss than the inverter, as configured for this test. A slight improvement 

in low power suppression would result for the internal mixer relative to the inverter for 

equal in-flight thrust. 

At takeoff power the in-flight EPNL suppression values are 3 EPNdB for the internal mixer 

and 4 EPNdB for the inverter. Relative to static operation this represents a gain in suppression of 1 EPNdB for the internal mixer and a loss of 1 EPNdB for the inverter. At a jet 

velocity of 500 m/s the in-flight suppression of the two configurations is equal (about 3 

EPNdB). 

On the basis of these comparisons the inverted flow profile will produce about 1 EPNdB 

lower noise in flight than the internal mixer at takeoff power. At lower power settings 

the two concepts are basically equivalent. There is a trend indicated that increasing the 

primary jet velocity above 600 m/s will favor the suppression potential of the inverted flow 

profile. Higher jet velocities will tend to shift the static peak noise of the inverter to a 

higher angle where a more favorable flight effect will result. This will help in reducing the 

in-flight EPNL in relation to the baseline and internal mixer. This is of importance to AST 

engines where primary jet velocities of about 760 m/s will be required during takeoff operations. 

5.5 INVERTER/PLUG ANALYSIS 

5.5.1 STATIC DATA ANALYSIS 

Static data for the inverter/plug configuration are compared with the baseline and inverter 

configurations in figures 63 to 65. The spectra plots of figure 63 show that only a slight 

reduction of SPL occurs relative to the baseline at low angles. The reduction at higher 

angles (figure 64) is more substantial at all frequencies. When compared with the inverter 

spectra the inverter/plug produces lower high frequency noise (figure 65). The low frequency noise at angles near the jet axis (140’) is slightly higher, however. 

OASPL and PNL directivities are compared in figure 65 for a NPR of 2.2. The inverter/plug 

produces lower noise in the low angle region primarily because of the reduced high frequency noise. The inverter/plug peak PNL suppression is slightly greater than the inverter 

(6.0 versus 5.5 PNdB). The peak OASPL suppression of the inverter/pIug is slightly less 

(5 versus 6 dB). At angles near the jet axis the inverter produces lower OASPL and PNL 

than the inverter/plug. This is the result of reduced low frequency noise in this region that 

is generated by the inverter. 

5.5.2 WIND TUNNEL DATA ANALYSIS 

Wind tunnel test results for the inverter/plug are provided in figures 66 to 70. Tunnel-off 

and tunnel-on spectra are compared in figure 66 for an NPR of 2.1 and a range of angles 

from 60’ to 150’. In general, the effect of tunnel velocity on the inverter/plug spectra is 

comparable with the inverter (figure 34);.that is, relatively small reduction of SPL at low 

angles with increasing reduction at higher angles. 

22 
Tunnel-off and tunnel-on OASPL and PNL directivities are shown in figure 67 for NPR’s 

of 2.1 and 1.8. Tunnel velocity causes a small reduction of OASPL and PNL at low angles 

(50’ to 100’). The amount of reduction increases at higher angles with maximum reduction occurring in the 140’ to 145’ range. Velocity index values are calculated from the 

results of figure 67 and are plotted in figure 68. At an NPR of 2.1 and 649 m sideline the 

velocity exponent values for the inverter/plug at low angles are slightly greater than the 

values for the inverter (figure 38~). At high angles the inverter n values are larger indicating 

greater reduction of noise with forward velocity in this region relative to the inverter/plug. 

OASPL and PNL are plotted as a function of primary relative velocity in figure 69 for 

several angles. The reduction of OASPL and PNL with tunnel velocity follows relative 

velocity at high angles (figure 69~) but not at low angles (figures 69a and 69b). This result 

is consistent with trends observed for the inverter configuration (figure 5 1). 

Static and flight EPNL’s are plotted versus primary relative velocity in figure 70. The 

relationship of the flight EPNL values with the throttle line is similar to results obtained for 

the inverter (figure 52). Static and flight OASPL, PNL and EPNL characteristics of the 

inverter/plug are compared with the baseline and other inverter configurations in section 5.7. 

5.6 INVERTERMIXER ANALYSIS 

The inverter/plug configuration was tested with a 20 lobe external mixing nozzle. This 

configuration was tested with and without an acoustically lined shield that was designed to 

reflect and absorb pre-merged mixing noise (see figures 6 and 7). Results and analysis for 

both mixer configurations are presented and described in this section. 

5.6.1 STATIC DATA ANALYSIS 

Static spectra comparisons are made for the baseline and inverter/mixer configurations with 

and without shield in figure 7 1. The 20 lobe nozzle configuration produces a large reduction in low frequency noise relative to the baseline, in particular at angles near the jet axis 

(figure 7 1 b). A significant component of pre-merged mixing noise is generated by the 

mixing between the primary jets and the entrained ambient air. This frequency component 

is centered at about 1250 Hz and causes a crossover of noise relative to the baseline at the 

lower angles (figure 7 1 a). The lined shield markedly reduces the pre-merged mixing noise 

component at all angles. The greatest reduction (up to 10 dB) occurs at angles near the jet 

axis (1 40°, figure 7 1 b). The reduction is also considerable at low angles (figure 7 1 a) with 

the pre-merged component lowered by about 5 to 6 dB. The shield is least effective in the 

region of peak noise (1 20°, figure 7 1 b) where only 2 to 3 dB reductions are observed. It 

is known from model tests that the effectiveness of a shield is very sensitive to shield size, 

orientation, and spacing relative to the noise source. It is likely that a shield of similar 

dimensions could be designed to more effectively reduce the pre-merged noise in the region 

of peak noise. There is also a change in low frequency noise that results when the shield is 

installed. The shield causes an increase in the low frequency noise at low angles (figure 

7 1 a). This may be caused by a slight directivity change in the shielded jet since the jet is 

turned toward the shield. The jet turning is the result of low pressure created between the 

jet and shield by the jet pumping process. 

23 
Static OASPL and PNL directivities are provided in figure 72 for the baseline and 20 lobe 

mixer configurations. The comparison reflects an NPR of 2.2 and a sideline of 649 m. 

The mixer is an effective suppressor of OASPL, relative to the baseline, at all angles. A peak 

OASPL suppression of about 9.5 dB is achieved. The shield has a small effect on OASPL 

providing an additional 1 dB reduction in peak OASPL. The mixer provides little suppression of PNL at low angles (50’ to 1 loo) but substantially reduces PNL at the higher angles. 

The peak PNL suppression is 5 PNdB; however, the suppression at 140’ is about 9.5 PNdB. 

The shield is effective in reducing the PNL at all angles but shows more reduction at offpeak noise locations. The peak PNL suppression of the shielded configuration is about 7.5 

PNdB while the suppression at 140’ is 13 PNdB. 

5.6.2 WIND TUNNEL DATA ANALYSIS 

Tunnel-off and tunnel-on takeoff power spectra are compared for the 20 lobe mixer in 

figure 73 and for the mixer with shield in figure 74. Wind tunnel velocity reduces the low 

frequency noise at high angles by a substantial amount (figure 73~). At low angles (figures 73a and 73b) the low frequencies are reduced by a modest amount. The pre-merged 

mixing noise component undergoes a slight increase (figure 73a) or slight decrease (figures 

73b and 73~) with tunnel velocity, depending upon angle. The effect of tunnel velocity 

on the mixer with shield configuration is quite similar to the effect on the mixer without 

shield (figure 74). 

Tunnel-off and tunnel-on OASPL and PNL directivities are provided in figures 75 and 76 

for the 20 lobe mixer without and with shield. The data reflect an NPR of 2.1 and a sideline of 649 m. At low angles forward velocity has little effect on the OASPL or PNL of 

the 20 lobe mixer configuration (figure 75). At angles from 50’ to 60’ a slight increase in 

noise results while at angles from 70’ to 100° a slight decrease in noise occurs with increasing tunnel velocity. A modest reduction of peak noise is observed with larger reductions at angles near the jet axis. The same trends with tunnel velocity are observed for 

the 20 lobe nozzle with shield (figure 76). 

The results of figures 75 and 76 and similar data for NPR 1.8 are used to define the velocity 

exponent curves of figures 77 and 78. In genera1 the velocity exponent characteristics for 

the 20 lobe nozzle with shield are superior to the configuration without shield. The 

shielded configuration produces higher velocity exponents at angles of 120’ and above for 

the takeoff power condition (figures 77a and 78a). This is the result of the lower premerged mixing noise in the shielded spectra (figure 7 1 b) where both OASPL and PNL are 

dominated by low frequency. The low frequency noise experiences a more favorable 

flight effect than the higher pre-merged frequencies that are more dominant in the spectra 

of the mixer without shield. 

Tunnel-off and tunnel-on OASPL and PNL values are plotted as a function of primary 

relative velocity in figures 79 and 80 for the 20 lobe mixer without and with shield. For the 

mixer without shield the reduction of OASPL and PNL with tunnel velocity is small at low 

angles compared with the throttle line (figure 79a). At 60° and high power the noise is 

observed to increase slightly with forward velocity. At 140’ and 150’ (figures 79c and 

79d) the tunnel-on data follow a slope close to that of the throttle line. That is, the inflight OASPL and PNL can be predicted by applying the relative velocity principle. The 

relative velocity trends for the mixer with shield are basically the same as those observed 

for the mixer without shield (figure 80). 

24 
Static and flight EPNL’s are plotted versus primary relative velocity in figures 81 and 82 

for the two 20 lobe mixer configurations. In each case the flight EPNL shows a significant 

departure from the throttle line. This is the result of the small reductions in PNL at low 

angles through peak that occur with forward velocity. 

Static and flight OASPL, PNL, and EPNL for the 20 lobe mixer with and without shield 

are compared with the baseline, inverter, and inverter/plug configurations in section 5.7. 

5.7 ~~MPARI~~NoFSTATICANDFLIGHT 

NOISEOFINVERTERCONFIGURATIONS 

Static and flight OASPL, PNL, and EPNL comparisons are provided in figures 83 to 86 for 

the family of inverter configurations evaluated in this report. The static noise levels are 

based on Boardman 30.5 m (100 ft) sideline data that are extrapolated to a 649 m (2128 ft) 

sideline using source location correlations. The flight noise levels are based on 40 by 80 

wind tunnel results and are defined by applying velocity exponents to the static data. 

Peak suppression values for OASPL, PNL, and EPNL are defined relative to the baseline 

and are summarized in table 3. 

5.7.1 OASPLDIRECTIVITYCOMPARISON 

Static and flight OASPL directivities are compared in figure 83 for the various inverter 

configurations. Under static conditions the peak OASPL suppression ranges from 5.0 dB 

for the inverter/plug to 10.5 dB for the inverter with 20 lobe mixer nozzle plus shield 

(table 3). The in-flight peak OASPL suppression ranges from 5.0 dB for the 20 lobe nozzle 

to 7.0 dB for the 20 lobe nozzle with shield. The inverter/plug peak OASPL suppression 

is slightly higher in flight than under static conditions (6 versus 5 dB). The biggest loss of 

peak OASPL suppression due to flight is experienced by the 20 lobe nozzle in going from 

9.5 to 5 dB. In general, the inverter family provides significant OASPL suppression at 

angles of 1 20° and higher during flight. The OASPL suppression at lower angles (50’ to 

110’) is modest. 

5.7.2 PNLDIRECTIVITYCOMPARISON 

Static and flight PNL directivities are compared in figure 84 for the inverter configurations. 

During static operation the peak PNL suppression varies from 5 PNdB for the 20 lobe 

nozzle to 7.5 PNdB for the 20 lobe nozzle with shield. Forward velocity causes a significant 

loss in peak noise suppression. The in-flight suppression values range from 0.5 PNdB for the 

20 lobe nozzle to 3.5 PNdB for the inverter/plug. The loss of peak PNL suppression varies 

from 2.5 PNdB for the inverter/plug to 4.5 PNdB for the 20 lobe nozzle with and without 

shield. 

The relatively low in-flight peak PNL suppression values are primarily the result of where 

the static peak PNL’s occur. The inverter configurations have peak PNL’s at relatively low 

angles (1 loo to 1 20°) compared with the baseline (135O). The reduction in PNL with 

forward velocity is considerably less at low angles than at high angles. For this reason the 

inverter configurations experience a significant loss of peak noise suppression due to flight. 

25 
The in-flight PNL suppression of the inverter configurations is substantial at angles of 1 30° 

and higher. At low angles (50’ to 110’) these configurations are not effective in reducing 

PNL relative to the baseline. 

5.7.3 EPNL SUPPRESSION COMPARISON 

Static and flight EPNL comparisons are.made for the inverter configurations in figures 85 

and 86. The static EPNL results of figure 85 assume that PNL’s, measured under static 

conditions, are not changed with forward velocity. The resulting static EPNL suppression values range from about 5 EPNdB for the basic inverter to nearly 10 EPNdB for the 

inverter/20 lobe nozzle with acoustic shield at takeoff power (600 m/s). 

Under flight conditions (figure 86) the inverter, inverter/plug, and inverter/20 lobe nozzle 

all have EPNL suppression values of about 4 EPNdB at takeoff power. The largest in-flight 

suppression is provided by the 20 lobe nozzle with acoustic shield (7.5 EPNdB). Although 

the in-flight EPNL suppression is less than static, the loss is relatively modest. The EPNL 

suppression is 1 EPNdB lower for the basic inverter and 3 EPNdB lower for the 20 lobe 

nozzle in going from static to flight conditions. 

It is evident from the comparison of figure 86 that the 20 lobe nozzle with acoustic shield 

has considerable potential for reducing in-flight EPNL. This potential is the result of rapid 

mixing of the high velocity primary with ambient air and subsequent removal of the high 

frequency pre-merged mixing noise. The 20 lobe nozzle without shield is not effective at 

low power but improves significantly as the primary velocity increases. At high primary 

velocity the post-merged mixing noise becomes more dominant in relation to the pre-merged 

mixing noise. The resulting flight effects are more favorable and the in-flight suppression 

potential of this configuration improves. At an extrapolated primary velocity of 650 m/s 

the EPNL suppression of the 20 lobe nozzle is estimated to be 1 EPNdB greater than the 

basic inverter. This favorable trend with increasing primary velocity makes the 20 lobe 

nozzle (or similar external mixing nozzle) more attractive for application with high velocity 

engines such as those being studied for AST. 

5.8 ENGINE/INVERTER DUCT PERFORMANCE 

Thrust performance characteristics of the inverter configurations are compared in figure 87. 

The performance is presented as thrust coefficient (CV) versus pressure ratio of the mixed 

flow. The thrust data were measured during the Boardman static test with a bell mouth 

inlet replacing the two ring acoustic inlet. At takeoff power (PTM7/P,b = 2.1) thrust loss 

values are 1.5% for the basic inverter, 3.0% for the inverter/plug, and 5.0% for the inverter/ 

20 lobe nozzle relative to the baseline (figure 87a). The 20 lobe nozzle with shield was not 

tested with a bell mouth inlet. Performance characteristics of the 20 lobe nozzle with and 

without shield are compared in figure 87b where both configurations included the two ring 

inlet. No significant difference in thrust coefficient is evident due to the presence of the 

shield. It is noted that force balance data were not measured during the 40 by 80 test; thus 

the effect of forward velocity on thrust performance is not known. 

Representative results of the inverted flow total pressure and temperature surveys are provided in figures 88 to 90. The data are for a takeoff power (NPR 2.1) and are typical of 

26 
results obtained at other engine power conditions. Lines of constant total pressure are 

plotted in figure 88 for one quadrant of the nozzle exit station. The lobe formation is 

typical of this type of flow ducting. An assessment of total pressure loss due to the inverter 

duct is difficult to make from these measurements. On the basis of the thrust coefficient 

loss for this configuration (1.5%) it is estimated that the effective total pressure loss of both 

streams is 2.5 to 3.0%. 

The total temperature data of figure 89 show that the high temperatures associated with the 

primary are confined to the outer flow region. The temperature profile in this region is far 

from uniform and indicates a lobe characteristic similar to the total pressure results of 

figure 88. The temperature lobe is caused by heat transfer between the primary and fan 

streams within the inverter duct and downstream of the duct prior to exhausting from the 

nozzle. 

The total pressure and temperature data are combined to define the exhaust velocity plot 

provided in figure 90. The lobe characteristic is evident in the outer flow region and reflects 

similar results obtained for both total pressure and total temperature profiles. The influence 

of the non-uniform flow region on noise characteristics is difficult to assess but is probably 

minor. 

5.9 MODEL RESULTS 

Model tests were conducted by Boeing prior to the JT8D engine inverted flow program. 

The one-seventh scale models were tested under static conditions to determine the influence 

of flow profile on jet noise characteristics. Some of the model data are included in figures 

9 1 and 92 for comparison with full scale results. Model OASPL and PNL directivities are 

shown in figure 91 for the baseline (uninverted), mixed, and inverted flow profiles. The 

results are for a takeoff power condition and a 457 m sideline. Similar OASPL and PNL 

directivity curves are provided for the full scale engine in figures 59 and 60, but for a 649 m 

sideline. The model data indicates larger OASPL and PNL suppression than the full scale 

data for both the inverter and internal mixer. Recent findings show that the baseline model 

data is high by several dB relative to the suppressors. This is based on comparisons with 

full scale results and recent model tests in a new facility. The model OASPL directivity 

characteristics of the internal mixer relative to the inverter are similar to full scale results 

(figures 91 and 59). The same comparison for PNL directivity indicates significant differences between model and full scale results (figures 9 1 and 60). The full scale data show 

the inverter PNL’s to be lower relative to the internal mixer at angles up to about 150’. 

Model and full scale peak PNL values are plotted versus velocity ratio in figure 92. The 

model data indicate minimum PNL at a partially inverted velocity ratio. A partially inverted 

flow profile assumes that the interchange of primary and fan streams is not complete. Thus 

the average outer flow velocity is slightly less than the fully inverted primary velocity while 

the average inner velocity is slightly greater than the fully inverted fan velocity. The full 

scale results show that the peak noise of the fully inverted flow is lower than the fully 

mixed flow. This finding is not necessarily contrary to the model results. The model 

velocity profiles were relatively more uniform than the full scale profiles for a given outer or 

inner velocity regime. The engine internal mixer did not provide a uniform, fully mixed 

flow nor the inverter a uniform inverted profile. The resulting unique flow profiles for the 

27 
internal mixer and inverter could explain the different model and full scale curve shapes in 

figure 92. For example, the poorly mixed, high velocity regions in the internal mixer flow 

could raise the peak PNL relative to a uniform profile. In contrast, the non-uniformity of 

the inverted profile may be representative of a partially inverted flow and cause a reduction 

in peak PNL relative to a uniform, fully inverted profile. These two occurrences would 

justify the shape of the full scale curve. In effect, the full scale internal mixer and inverter 

data points are plotted at an invalid velocity ratio and should be shifted toward the right in 

figure 92. The magnitude of the shift is difficult to evaluate but would be in a direction to 

make the model and full scale curves more alike. 

The model and full scale comparisons indicate that model profile tests can be used to 

indicate general trends. Full scale engines designed for a unique profile will likely include 

significant non-uniformities in flow profiles. This may make accurate predictions of full 

scale noise levels from model resu1t.s difficult to achieve for both static and flight conditions. 

28 
6.0 CONCLUSIONS 

The following conclusions are made as a result of the test program to determine static and 

wind tunnel-derived flight noise characteristics of the JT8D-17R engine with inverted 

primary and fan flows. The suppression results described are relative to the baseline configuration (uninverted flow) and reflect takeoff power at a 649 m sideline. 

1. 

2. 

3. 

4. 

5. 

1. 

2. 

6.1 BASIC INVERTER 

The basic inverter configuration (inverter with conical nozzle) provides an in-flight 

EPNL suppression of 4.0 EPNdB. The comparable static suppression (summation of 

static PNL’s) is 5.0 EPNdB, indicating a relatively modest loss of EPNL suppression 

due to flight. 

Forward velocity causes a significant loss of peak PNL suppression. The in-flight peak 

PNL suppression is 2.5 PNdB compared with a static value of 5.5 PNdB. The inverter 

is effective in suppressing PNL at angles of 130’ and higher but ineffective at lower 

angles where the inverter peak noise occurs. 

The influence of forward velocity on OASPL suppression is relatively small. The peak 

OASPL suppression changes from 6.0 dB to 5.5 dB in going from static to flight conditions. Significant in-flight OASPL suppression is achieved at angles of 120’ and higher. 

Suppression of OASPL at lower angles is modest. 

The inverted flow provides lower EPNL than the mixed flow under both static and 

flight conditions. Static EPNL suppression is 5.0 EPNdB for the inverter and 2.0 

EPNdB for the internal mixer. The in-flight suppression values are 4.0 and 3.0 EPNdB 

respectively. 

The inverter configuration experienced a thrust loss of 1.5% relative to the baseline. 

The lower thrust is largely due to total pressure losses in the primary/fan inverter duct. 

6.2 INVERTER/PLUG 

Replacing the conical nozzle with a plug nozzle produced minor reductions in the 

flight noise levels determined for the basic inverter. Improvements in peak OASPL and 

PNL suppression values were 0.5 dB and 1 .O PNdB respectively. The in-flight EPNL 

suppression was virtually the same for the two nozzle configurations. 

The inverter/plug had a thrust loss of 3.0% compared with 1.5% for the basic inverter. 

The additional thrust loss may have contributed to the slightly lower noise levels 

generated by this configuration. 

29 
6.3 INVERTER/20LOBEMIXER 

1. The inverter with 20 lobe mixer nozzle provided improved static EPNL suppression 

when compared with the basic inverter (7.0 versus 5.0 EPNdB). In-flight suppression 

values were equal indicating a larger loss of EPNL suppression for the 20 lobe configuration with forward velocity. 

2. The inverter with 20 lobe nozzle and lined acoustic shield produced the lowest EPNL 

for both static and flight operation. A static EPNL suppression of about 10 EPNdB 

was achieved while the flight suppression was 7.5 EPNdB. The improved suppression 

was caused by the absorption and reflection of high frequency pre-merged mixing 

noise. 

3. The thrust loss of the 20 lobe nozzle configurations was 5%. The thrust loss, weight, 

and design integration factors must be considered in evaluating potential applications 

for this suppressor concept. 

6.4 MODELRESULTS 

1. Static model data for the JT8D baseline, internal mixer, and inverter indicate trends 

similar to those measured for the full scale engine. This includes OASPL and PNL 

directivities and peak PNL as a function of flow profile velocity ratio. Some differences in model and full scale results are noted, but are generally explainable due 

to non-uniformity in the full scale flow profiles. 

30 
REFERENCES 

1. Strout, F. G.j Flight Effects on Noise Generated by the JT8D-17 Engine in A Quiet 

Nacelle and a Conventional Nacelle as Measured in the NASA-Ames 40- by 80-Foot 

Wind Tunnel, NASA CR-l 37797, January 1976. 

2. Strout, F. G., Flight Effects on Noise Generated by the JT8D-17 Engine in a Quiet 

Nacelle and a Conventional Nacelle as Measured in the NASA-Ames 40-by go-Foot 

Wind Tunnel - Summary Report, NASA CR-2576, June 1976. 

3. Jaeck, C. L., Static and Wind Tunnel Near Field/Far Field Jet Noise Measurements 

from Model Scale Single-Flow Baseline and Suppressor Nozzles - Summary Report, 

NASA CR-2841, June 1977. 

31 
Table I.-Acoustic Test Conditions and Microphone Locations for Boardman Static Test 

Configuration 

Baseline 

lnverter 

Inverter/Plug 

Inverter/Mixer 

Inverter/Mixer/Hard Shield 

Inverter/Mixer/Lined Shield 

Microphone sideline 

3.05m (loft) 

15.2 m (50 ft) 

30.5 m (100 ft) 

Type 

C/L 

ground 

Nozzle pressure ratio 

1.05; 1.1; 1.2; 1.3; 1.4; 1.5; 1.6; 1.7; 1.8; 1.9; 2.0; 2.1; 2.2 

1.05; 1 .l; 1.2; 1.3; 1.4; 1.5; 1.6; 1.7; 1.8; 1.9; 2.0; 2.1; 2.2 

1.05; 1.1;1.2;1.3; 1.4; 1.5; 1.6; 1.7; 1.8; 1.9;2.0;2.1;2.2 

1.05; 1.1; 1.2; 1.3; 1.4; 1.5; 1.6; 1.7; 1.8; 1.9; 2.0; 2.1; 2.2 

1.1; 1.4; 1.6; 1.8;2.1;2.2 

1.1; 1.4; 1.6; 1.8; 2.1; 2.2 

Microphone angle 

30’. 40°, 50’. 60’. 70°, 80°, 90’. 100°, 110’ 1 20°, 130°, 

140’. 150’. 155’, 160’. 165’ 

30’. 40°, 50’. 60’. 70°, 80°, 90°, 1 OO’, 1 IO’, 1 20°, 130’. 

140°, 150°, 155’, 160’ 

50’. 60’. 70°, 80’. 90°, 100’. 11 O”, 120’. 130°, 140’. 

1 5o”, 155O 

Table 2.-Test Conditions for 40- bv 80-Foot Wind Tunnel Test 

Configuration 

lnverter 

Inverter/Plug 

Inverter/Mixer 

Inverter/Mixer/Shield 

lnverter and Inverter/Mixer 

Inverter/Mixer/Shield 

Tunnel velocity 

(knots) Nozzle pressure ratio 

0 1.1; 1.3; 1.4; 1.5; 1.6; 1.8; 1.9; 2.1 

100 1.1; 1.4; 1.6; 1.8 

150 1.6; 1.8;2.1 

185 2.1 

0 1.3; 1.4; 1.6; 1.8; 2.1 

100 1.4; 1.6; 1.8 

150 1.6; 1.8; 2.1 

185 2.1 

0 1.3; 1.4; 1.6; 1.8;2.1 

100 1.4; 1.6; 1.8 

150 1.8; 2.1 

185 2.1 

0 1.4; 1.6; 1.8;2.1 

100 1.6; 1.8 

150 1.8; 2.1 

100 1 .O - Noise Floor 

150 1.0 

185 1 .o 

100 1.0 

32 
Table 3. -Summary of In verter Suppression Characteristics 

.-_- OASPL suppressron-db 1 PNL suppression-PNdl3 EPNL suppression-EPNdB 

Configuration [K( Flight 1 Change 1 Static Flight Change Static Flight Change 

-0.5 5.5 2.5 -3.0 5.0 4.0 -1.0 

Inverter/Plug 6.0 3.5 -2.5 5.2 4.0 -1.2 

Inverter/20 Lobe -4.5 5.0 0.5 -4,5 7.0 4.0 -3.0 

Inverter/20 Lobe -3.5 7.5 3.0 -4.5 9.8 7.5 -2.3 

with Lined Shield 

Note: Peak noise suppression relative to baseline at takeoff power and 649m (2128 ft) sideline 

33 

-. 
,. .,’ , 

,,‘,.. 

I I 

Figure I.-Static Test Installation, lnverter Configuration 
II 

BASELINE 

ACOUSTICALLY CONICAL NOZZLE 

TREATED INLET 

INVERTERfPLUC 

LINVERTER DUCT 

CONICAL PLUG 

INVERTER/MIXER 

AND WITHOUT SH 

L20 LOBE NOZZLE 

Figure 2.-Test Configuration Schematic 

35 
w 

ch 

Figure 3.-Primary/Fan Flow lnverter, Exit Station 
Figure I.-Test Installation in 40 by 80 Wind Tunnel 
Figure 5. --In verter/Plug Configuration 

38 
39 
Figure 7.-lnverter/20 Lobe Mixer Configuration with Acoustic Shield 

40 
FRLO 200 -I 

t140- 

iI 

d 

ii 

ilOO1 

;: 

2 

L , L L - iI Y 

WC AXIAL fTATION-lh llfO-a, 

* f 

Il30- FREO 250 

I I I -2 -1 I I 2 3 4 5 6 

WCAXIALSTATlON-lh~1W-~~ 

(a) Freq 200 & 250 

Figure 8.-Multiple Sideline SPL Directivity JT8D- 17R Engine with lnverter Configuration 

41 
.--- 

a FIEQ 800 

. . 

UL %a6 ni - C/L YIC 

1f.f m ORD YIC 

fO.f~ORDYlC 

B 

z 

5 

g IOL I 

-2 -1 0 1 2 3 4 5 6 

YICAXIAL STATION- l/a IlW -81 

FRED 1000 

ULLmm-CILWC 

1f.f Ill cm MIC 

a0.f II) CRD YIC 

f,,l , , , , , , , , 

-2 -1 0 I 2 3 4 S 6 

WtC AXIAL ITATIOII - 1/9n 11m - 61 

(b) Freq 800 & 1000 

Figure 8. -(Continued) 

42 
e4 

5,30- 

t 

d 

P 

;120- 

1 

d 

5 

PIlOI 

rREO 3150 

UL JJtim-ULMIC 

I&!2 m GRD YIC 

i IOO- ~nORDYlC 

; 

z IOE 

i 

t 

% go- I I I 

-2 -I 0 I 2 3 4 5 6 

floot d 

ii 

;120- 

1 

;: 

> 

!t 

$oP 

,' 

$100. 

s 

2 

I- BO8 

B 

5 

Ml.2 AXIAL STATION - 1h.n (180 - 81 

FREO 4000 

YL J.m Ill - C/L MIC 

,622 m GRD YIC 

303 m GllD MIC 

I 1 I I I I 

-2 -I 0 1 2 3 4 3 6 

YIC AXIAL STATION-lllln tlw) - 81 

(c) Freq 3150 & 4000 

Figure 8.-(Concluded) 

43 
(a) Freq 200 Hz & 250 Hz 

Figure 9. -Determination of Noise Source Location, In verter Configuration 

44 
(b) Freq 800 Hz & 1 K Hz 

Figure 9. -(Continued) 

45 
(c) 3150 Hz & 4K Hz 

Figure 9. -(Concluded) 

46 
200 Hz 

S/N - .276 

) 5 O II 20 40 I60 I ‘80 1 100 I 120 1 140 I 160 1 

210 - 

2 

w 22 250 Hz 

z 

S/N = .345 

* 8- 

: 

H 

6- 

4- 

2r ” 

O 

L I L 1 I I I I -’ 20 --- 4a 60 80 100 120 140 160 

NOISE EMISSION ANGLE-es-deg 

(a) 200 & 250 Hz 

Figure lo.- Noise Source Location versus Emission Angle, lnverter Configuration 

47 
8 

800 Hz 

S/N = 1.105 

6- 

4- 

e* 2 - 

‘; r% h 

8 

5 

I 

2 

I 

O 20 

I I I I 

40 60 80 100 1;o ,a0 iA0 

OL20 

1 I I I I I I I 

40 NOI% EMISSI~ 100 120 140 160.- 

ANGLE-OS- deg 

(b)800&1 KHz 

Figure 7 0. -(Continued) 

48 
10 - 

3150 Hz 

S/N - 4.351 

8- 

6- 

j: 

g I 

& O 20 

I I I I I I I 

--- 40 60 80 100 120 140 160 

210 - 

v) 

is 

% 

4000 Hz 

8- S/N = 5.525 

6- 

:r _ ;/ 

. 

O ;o 

I I I I I I I 

40 60 80 100 120 140 160 

NOISE EMISSION ANGLE-Gs-deg 

k)3150&4K Hz 

Figure 10. -(Concluded) 

49 
. 

S/N = 0.06 

HPE 

n 2.2 

0 .2.0 _ 

0 1.8 

A 1.6 

0 1.4 

--... - 

. 

61 .: - -_ -_._ 

(a) S/N = 0.06 & 0.20 

Figure 1 I.-Noise Source Location Correlation for lnverter Configuration 

50 
I S/N = 0.75 

8- 

. . _ _ 6 - __ -. - ._ ___ _ 

__._ _- __.. .- ..__ - ..- -_ 

3i.o 1 I I 1 I I I I -.- 

E 20 40 60 ,.. :..B?. . . . . ._ 

100 120 140 160 _ _ 

z 1°r ---. 

._ _ ___ .- _ - . - _,. ___.__ - --.+-- . _ - 

- 7.-.--. - -. 

-w 

% 

.____ -+ S,N II.40---‘-‘-. .L.. .-.--L.- 

-: . :__ . 

-.- -- 

8 --L--------b ..- - -.- - ‘. 

! - 

- _. .I. T- L- __ T.iT-l-- ._____: ___._ ._---.- -~.--~ -_. - - _._ --- 

._... -I _ ._.._._ !__ _.. ..-:.-’ -.1 - 

: 

i .-.:’ --’ 

: . 

_ ._ _. ___I 1- .--.- --. --.. - 

lb1 S/N = 0.75 & 1.40 

Figure 11.42ontinued) 

51 
10 

r 

‘I 

8 S/N = 3.00 

- I-- _ _ 

4 __ _., __. _. __I _- _ :_ ..- _ _ _. _ _ _ 

: : _ . . 

_ _ _. .-.----.-.- _ __ _ _ . L _ _. . ._.. _ .- ._...._... A-. ._._ .-45 

.- .- ._..: 1 I I _- . 

80 100 120 .-I _. . . _.: -140. _ 160 ..i 

.glo 

: 

: 

.._ _. _ _- .____ _ -- .._.___ L... .- - --,- _ . . _ . - . . -. _-._ _. -. 

s 

- i 

. 

,_ 

.._ . 

: 

.__ -_.. ___--.- .- -- --. _- - 

z 

z r 8 

(c) S/N = 3.00 61 12.00 

Figure 1 l.-(Continued) 

52 
(d) S/N = 30.00 

Figure 11. -(Concluded) 

- .- 
ul 

P 

REAR'FIELD SPL AD.IUSTkQ 

- PEAK FAR FIELD S?L (30'.5 m) 

- PEAR NEAR FIRLD SPL EXTRAhATED EXTRAhATED 

TO COtMN SIDELINE 

Figure 12.-Near Field SPL Adjustment 
% 100 

: 

2 

8 0 90 

d 

TUNNEL-OFF 

NPR 

2.1 

1.8 

1.6 

1.4 

I . . I. .I . . I.. 1 . . I I . I I. 1 *. I 

* 50 loo 200 400 800 1600 3150 6300 12600 

100 KNOTS 

,--\ 

L1.4 

/' 'I/ 

_-I-- \ 

'\ 

/ '\ / .,4x 

/ \ /--\ 

r- -1-,' \ 

.\ 

'.l.l 

7o I,... ..l..r,.l..l..l..l..I 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) Tunnel-Off & 100 Knots 

Figure 13.-Reverberant Field Spectra for lnverter Configuration 

55 

-. 
120 150 KNOTS 

110 

100 

2 

z 90 

2 

Q 

d 

. . 80 

z 

2 

.: 70 

1.6 

, *. 1 I .I .* I’.‘*-““““*( 

50 100 200 400 800 1600 3150 6300 12600 

185 KNOTS 

32.1 

1.1’..~1.““““.“.“,’ 50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(bl150 Knots & 185 Knots 

Figure 13. -(Concluded) 

56 
“ml = 550 m/r 

FREDUENCY - 100 Hz 

CONFIGURATION: INVERTER 

Bm SIDELINE 

DATA CORRECTED TO ZB% (77°F); 7B% RH 

d BDARDMAN DATA 

-d-40’ BY m TUNNELOFF DATA 

--*--%STMTED REVERBERANT FIELD 

j, 4il &I Ii-- 70 80 90 I loo 110 120 130 140 1Bo 1Ba 170 , 

ANGLE RELATIVE TO INLET AXIS - deg 

(a) Freq 100 Hz 

Figure 14.-Comparison of Free Field and 40 by 80 SPL Directivity, lnverter Configuration 

57 
vpR1= 550 m/s 

FREQUENCY - 200 Hz 

CONFIGURATION: INVERTER 

3m SIDELINE 

DATA CORRECTED TO ZB’C (7pF); 70% RH 

--c- BOARDMAN DATA 

--o-40 BY 80 TUNNELOFF DATA 

--*---ESTIMATED REVERBERANT FIELD 

8 4 

30 40 60 60 70 80 m loo 110 120 130 140 160 160 170 

ANGLE RELATIVE TO INLET AXIS - deg 

(b) Freq 200 Hz 

Figure 14. -(Continued) 

58 
128. 

124 - 

120 - 

96 - 

92 - 

88- 

%?I - 540 m/a 

FREQUENCY - 4~30 Hz 

CONFIGURATION: IWERTER 

3r1 SIDELINE 

DATA CORRECTED TO 2!5OC (77oF); 70% RH 

-c- BDARDMAN DATA 

-dk-40 BY BO TUNNEL-OFF DATA 

--+--ESTIMATED R!ZVERRERANT FIELD 

m 40 60 00 70 80 90 loo 110 

I 

120 130 140 1w lB0 170 

ANGLE RELATIVE TO INLET AXIS - deg 

(c) Freq 400 Hz 

Figure 14. -(Continued) 

59 
FREDUENCY - 800 Hz 

124 - 

120 - 

96 - 

92 - 

88- 

---------- 

CONFIGURATION: INVERTER 

3m SIDELINE 

DATA CORRECTED TO i?E°C (77oF); 70% RH 

-BOARDMAN DATA 

-h-40 BY 80 TUNNEL-OFF DATA 

--e-- ESTIMATED REVERBERANT FIELD 

j, 4fJ #) 60 70 80 90 loo 110 120 l#) 140 1Bo lB0 170 4 

ANGLE RELATIVE TO INLET AXIS - deg 

(dl Freq 800 Hz 

Figure 14.~(Continued) 

60 
lZ6r 

116 - 

94 - 

90 - 

86- 

FREQUENCY - 1600 Hz 

CONFIGURATION: INVERTER 

3m SIDELINE 

DATA CORRECTED TO 26% (77°F); 70% RH 

+KBARDMAN DATA 

-*-40’ BY SO TUNNEL-OFF DATA 

--X----ESTIMATED REVERBERANT FIELD 

, 

30 

‘ 

40 w so 70 so so loo 110 120 130 140 150 100 170 

ANGLE RELATIVE TO INLET AXIS - deg 

(a) Fraq 16GO Hz 

Figure 14. -[Con timed) 

61 
6~ 

2- 

E4- 

O12’ 

12 

11' 

"C 

1 =11 

d 

I i 11 

i 

0 

iI 

10 

z 

!3 

10; 

z 

f 9e 

B 

94 

9c 

6- 

zI - 

1 - 

)- 

06- 

“#(I’ 550 m/s 

FREQUENCY = 3150 Hz 

CONFIGURATION: INVERTER 

3m SIDELINE 

DATA CORRECTED TO 26% (WF); 7% RH 

+ BOARDMAN DATA 

-+-40’ BY SO TUNNEL-OFF DATA 

---W--ESTIMATED REVERBERANT FIELD 

j, 40 60 00 70 80 so loo 110 120 130 140 150 160 170 I 

ANGLE RELATIVE TO INLET AXIS - deg 

(f) Freq 3150 Hz 

Figure 14.~(Concluded) 

62 
Hm16 - 

0 

A 

i 

0 

: 

2.1 = NPR 

1.8 

1.6 

1.6 

1.5 

1.4 

1.3 

1.1 

SOLID SYMBOLS ADJUSTED FOR 

A PEAK 0 RELATIVE TO NPR = 2.1 

I * .I.. 1 I. I.. I a * I. I I I I I I. 

50 loo 200 400 606 1600 3150 63m &lo 

ONE-THIRD OCTAVE BAND CENTER FREDUENCY- Hz 

Figure lh-Relationship of Reverberant Field SPL to Peak SPL, lnverter Configuration 

63 
3.05 m SIDELINE 

NFR - 2.1 

. - 8" NIC SPETFA - TmJNn OFF 

--- 8' HIC SPECTRA - 15okn 

(CORRECTED FOR BACXGROUND NOISE) 

T'WNKL. OFF BEVERBERANTFIELDLEVEL 

DETERWINED FRm 40 by80AND BOARMAN DATA 

A TUNNELON RWFXBERANT FIELDLEVELBASEDON 

~NCREMEN'T FROM TUNNEL OFF 8' HIC SPECTRA 

(INC~NT I prim SPL Tmm~ OFF - pi5.w SPL TUNNEL ON) 

ONE-TEIRD OCTAVE BAND CENTER FREQUENCY - Hz 

Figure 16. -Comparison of Reverberant Field Spectra, In verter Configuration 

64 
120 f 7o" 

110 - 

100 - 

N 

5 

g goz 

d 

ii 8o 

z 

TUNNEL 

VELOCITY 

95 m/s 

(185 kn) 

80 m/s 

(155 kn) 

$' "I* Id0 .-. 200 " " 400 " 800 " " 1600 " 3150 "'I 6300 * 

Y 

* 12600 1 

/1 / \A \,’ ‘.,‘\ \ 

\ --.\ 

70 L I . . I I I I I I I I I I I I 

50 -100 

I , I 1 , , I , 

200 400 

, , 

800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

Figure 17. -Tunnel Background Noise Spectra 

65 
NPR - 2.1 

OASPL 

649m SIDELINE (2128 ft) 

102rSYMBOL lTmN=l 'JpRIl V- 1 s (UNITS PNL 

I I I I I 

---o-- 1 OFF 1 570 t 211 549 I m/s 

I 1 1870 1 701 1800 1 ft/S 

. t ON 1 570 1 831 487 1 m/s 

98- I 1 1870 1 2721 1598 I ft/s 

; 1 ON 1 ,,',"; 1 104) 457 I m/s ' 

I I 1 3401 1500 I ftls 

,@' 4 

\ 

5 

94 - 

a. 

86- 

82 , 1 1 1 1 4 20 40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(a) NPR = 2.1 

Figure 18.-Comparison of Tunnel-Off and -On OASPL and PNL Directivities, Baseline 

Configuration 

66 
92r NPR - 1.8 

OASPL 

88- 

8 84. 

I 

iz 

2 0 80. 

76. 

72Lic.. 4; 60 I A 100 I , I 

80 120 140 160 

SYMBOL I TUNNEL] VPRI I Va. 1 L'B /UNITS 

I I I 

489 I 19 I 470 1 m/s 2..,- PNL 

41b 1 h,. 

-"s \ 

I 

"\ 

649m SIDELINE (2128 ft) ,0= \ 

76 L 

;t. 

1 

40 60 80 100 120 140 160 

FAR PI!ZLD ANGLE RELATIVE TO INLET AXIS -deg 

lb1 NPR = 1.8 

Figure 18. -(Concluded) 

67 
. . - .- _._- .-- 

16- 

oOASPL 

649m SIDELINE (2128 ft) 

A n FROM 150kn DATA 

0 n FROM 185kn DATA 

I I t I 1 1 I I 

20 40 60 80 100 120 140 160 

PNL 

APNL 

” - 10 b3 VPRI/VR 

20 1 40 I 60 I 80 I 100 1 120 I I 

140 

160 I 

FAR FIELD ANGLE RELATIVE TO INLET AXIS -deg 

(a) NPR = 2.1 

Figure 19.-Velocity Exponents for OASPL and PNL, Baseline Configuration 

68 
16 

r 

OASPL 

c 

649m SIDELINE (2128 ft) 

A n FROM 150 kn DATA 

7 12 0 n FROU 185 kn DATA 

1 I I I 1 I 1 I 

20 40 60 80 100 120 140 160 

16 

" - 

A PNL 

10 Log VPRI/VR 

PNL 

I I I I I I I 

20 40 60 80 100 120 140 10 

FAR FIRLD ANGLE RELATIVE TO INLET AXIS .. deg 

(b) NPR = 1.8 

Figure 19.~(Concluded) 

69 
AIRCRAFT &STANCE: 649a (2128 ft) 

VBLOCITY: 91.5m/s (300 ft/s) 

BOARDMAN f0.5m DATA 

-2 E?NL WITHOUT FLIGHT EFtiECT 

PEOTTED VEUSUS VpRI 

---O-- - EPNL ~1~~40 by 80nICLT 

EFFECTS PLOTTED VERSUS (VpRI - Vo ) 

I 0 

200 300 400 500 600 

PRIMARY VELOCITY - VpRI OR WpRI - V, 1 - m/s 

2.2 

Figure 20. -Static and Estimated Flight EPNL Characteristics, Baseline Configuration 

70 
NPR - 2.1 

6d0 

80 - 

70 - 

% 

3 

2 

g 60. 

d 

. . 

Y 

G 50 - 

I 

ii 

2 40- 

BOARMAN STATIC DATA 

122m SIDELINE (400 ft) 

- 30.5m DATA 

---- 3.05m DATA 

a.. 1 . . 1 . - ’ s n ‘a. ‘1 1 ’ * * ‘* 1 J 50 100 200 800 1600 3150 6300 12600 

80' 

I I. 1. .I * * ’ - ‘1. * ’ * *“*I’ -’ 50 loo 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE RAND CENTER FREQUENCY - tlz 

(a) So0 & 80° 

Figure 21.-Comparison of Near and Far Field Spectra, lnverter Configuration 

71 
1OOr NPR - 2.1 

loo0 

7 1;; 

z 

E 

d 70- BOW STATIC DATA 

122m SIDELINE (400 ft) 

. . 1 - 30.510 DATA 

% ---- 3.05m DATA 

I 60 - 

ti 

5 

200 400 800 1600 3150 6300 12600 

120° 

60 

I 

* I 100 200 400 800 16 loo’ ’ I ’ I loo’ 3150 63 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b) 100°&1200 

Figure 21.-(Continued) 

72 
NPR - 2.1 

140° 

BOARIMAN STATIC DATA 

122m SIDELINE (400 ft) 

- 30.5m DATA 

---- 3.05m DATA 

L -a 1 - * 1 * * 1 * - 1. * 1.. 1 * * 1’. 50 100 200 400 800 1600 3150 6300 12600 

150° 

lla. 1 a II*. 1A.I. - 1. * I* -1. *I 

50 100 200 400 800 1600 3150 6300 12600 

ONE-TNIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(cl 140° & 1500 

Figure 2 1. -(Concluded) 

73 
N?lZ - 2.2 - OABPL 

92- 

A 

86 - i 0 

8 

84 - 4 

: 

I t 

i 80- 

z 

t 

BOARDnAN DATA 

649m SIDELINE (212'3 ft) 

76 - . 30.5m S/L DATA 

A 15.2~1 S/L DATA 

0 3.05~1 S/L DATA 

72L ’ f I I f I I J 

20 40 60 80 100 120 140 160 

90- PNL 

94 - 

0 

0 

02 

78 - 

4 

- I I 1 I 1 I 

20 40 60 80 100 120 140 160 

ANGLE RELATIVE TO INLET AXIS - deg 

(a) NPR = 2.2 

Figure 22.-Comparison of Near and Far Field OASPL and PNL Directivity, lnverter 

Configuration 

74 
NPR - 2..1 - OASPL 

BOARIMAN DATA 

649m SIDELINE (2128 ft) 

l 30.5m S/L DATA 

A 15.2m S/L DATA 

0 3.05111 S/L DATA 

LJ 7o 20 

I I I I I I 4 

40 60 '80 100 120 140 160 

96- 

PNL 

92 - 

s 

00 - 

76: ' I I I I 1 I J 

20 40 60 80 100 120 140 160 

ANGLE RELATIVE TO INLET AXIS -deg 

(b) NPR = 2.1 

Figure 22. -(Con timed) 

75 
86- NPR - 1.8 - OASPL 

82- 

0 : 

: t : 

R 

A I 

m 70- 

-a 

i 

0 74- 

I 

t 

BOARDMAN DATA 

649m SIDELINE (2128 ft) 

'70 - 0 30.51~ S/L DATA 

A 15.h S/L DATA 

@ 3.0h S/L DATA 

66 I I I I I 1 I J 20 40 60 80 100 120 140 160 

92r 

80- 

PNL 

: 'g * 

t A 

A 

t 

e t 

0 

72 2b 

I I I I 1 I 

40 60 80 100 120 140 lb0 

ANGLE RESTIVE TO INLET AXIS - deg 

Ic) NPR = 1.8 

Figure 22. -(Continued) 

76 
82~ 

78 - 

EUIARDMAN DATA 

649111 SIDELINE (2128 ft) 

66 

t 

. 30.5m S/L DATA 

A 15.h S/L DATA 

0 3.05m S/L DATA 

NPR - 1.6 - OASPL 

62lZb 1 40 I 60 I 80 L 100 I 120 I 140 L 160 I 

0a04- 

80 - 

: 

E 

t 

I 8 8 

rl 76- 

& 

t 

A 

e 

0 

72- 

68 I I I I 1 I I 1 

m 40 60 80 100 120 140 160 

ANGLE RELATIVE TO INLET AXIS - deg 

(d) NPR = 166 

Figure 22. -(Concluded) 

77 

.._. - ’ 
BOAW STATIC DATA 

85 649m SMELINE (2128 ft) 

- 30.5111 DATA 

--+--3.05m DATA 

60’ 

60 1 

, 

150 200 

I 

300 400 

PRIMARY VELOCITY VPRI - m/s 

500 660 

(a) 60°,900,1200 

Figure 23.-Comparison of OASPL versus Primary Velocity, 30.5 m and 3.05 m 

Data-In verter Configuration 

78 
~0~ STATIC DATA 

64% SIDELINE (2128 ft) 

.- 30.5m DATA 

159 

---o--- 3.05m DATA 

I 150 

I 200 700 400 500 43 

PRIMARY VELOCITY V,,, - m/s I 

(b) 140°, 155’ 

Figure 23. -(Concluded) 

79 
loo95- 

9c85- 

floi-5- 

10- 

BQARJIMAN STATIC DATA 

649m SIDELINE (2128 ft) 

----t-30.5m DATA 

--- 0 ---3.05m DATA 

I 

150 

1 1 

200 360 400 1 500 660 

PRIMARY VELOCITY VpRI - m/s 

(a) 90°, 90°, 120° 

Figure 24.-Comparison of PNL versus Primary Velocity, 30.5 m and 3.05 m Data-lnverter Con figuration 

80 
9ce5- 

70. 

65 

BOARDHAN STATXC DATA 

659m SIDELINE (2128 ft) 

- 30.510 DATA 

---o---3.'05m DATA 

140 200 L 300 I 400 I 

1 4 

500 600 

PRIMARY VELOCITY VpRI - m/s 

(b) WP, 155O 

Figure 24. -(Concluded) 

81 

-. - 
NPR - 2.2 

90 

r 

60' 

70 - 

N 

5 

0" 

g 60- BOARDMAN STATIC DATA (30.511,) 

0 12210 SIDELINE (400 ft) 

d V PRI 570 m/s (1895 h/s) 

. . 2 - BAS!X.INE 

50- --- INVERTER 

2 

I 

ti 

% 4o 50 lI~I..I..1.II,~JI~I..J.11 100 200 400 800 1600 3150 6300 1260Q a 

9o" 

50L 11,1~.l.I1111111'~'~~".( 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) So0 81 90° 

Figure 25.-Comparison of Baseline and lnverter Spectra: NPR = 2.2 

82 
2 

BOARDMAN STATIC DATA (30.5m) 

122m SIDELINE (400 ft) 

I 

ti 

VpRI 570 m/s (1895 ft/s) 

t 70 -BASELINE 

2 ---- INVERTER Ia2 

g 

$ 

6o 

L..l..l..l~.l *II,, I ,.,.,, k 50 100 200 400 800 1600 3150 6300 12600 

140° 

ijo LIIIII.I.1IIIIII11I1~~11I1 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b) 120°&1400 

Figure 25. -(Concluded) 

83 
NPR - 2.1 

5o" 

1lOr 

100 - 

. . 

Y 

z 70 - I 

g 

g 60*5a 100 1 . , 200 I . . 400 , , . 800 , 1600 I I * 3150 I * . 6300 , , , 12600 J 

2 110. 

e. 

P 

I 60' 

,o 

0 loo2 

BOABDMAN STATIC DATA (30.5~~) 

122m SIDELINE (400 ft) 

g V PRI - 550 m/s (1805 ft/sl 

2 - BASELINE 

8 go --- INVERTER 

60L50 1.. 100 I ..I,,,,.(,,, 200 400 800 1600 '3150' I ' 6300 ' ' ' ' 

Ok-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 12600 

(a) 50’ & 50’ 

Figure 26.-Comparison of Baseline and lnverter Spectra: NPR = 2.7 

84 
NPR - 2.1 

700 

; Bo.; 

ii 

70. 

2 

$60- ' 5a "'..'..'l.r..r..r..'..l 100 200 400 BOO 1600 3150 6300 12600 w 

BOARDMAN STATIC DATA (30.5m) 

122m SIDELINE (400'ft) 

g 

V PRI - 550 m/s (1805 ft/s) 

z 

- BASELINE 

---- INVERTER 

70 

t 

6o L,,.I..Il.I~.‘..‘l.‘,“‘.J 50 100 200 400 BOO 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b) 70’ & 80° 

Figure 26. -(Con tinued) 

85 
NPR - 2.1 

9o" 

110- 

100 - 

t 1::; 

. -- 

. . 

122m SIDELINE (400 ft) 

s 70. 'PRI - 550 m/s (1805 ft/s) 

c2 - BASELIN!i 

I ---- INVERTER 

ii 2 

2 60-".'*"'.'..".'."~.'~'J 50 100 200 400 800 1600 3150 6300 12600 

E 110 loo0 

E 

2 1 

z 

100 

Figure 26. -/Continued) 

86 
NPR - 2.1 

llo" 

. . 

2 

; 

I 

G 

5 70 6Ll ..#*. l nml.. l..ls.l..l 

w 50 100 200 400 800 1600 3150 6300 12600 

!z m 110' 

M 120° 

& BOARDMAN STATIC DATA (30.5m) 

B 122m SIDELINE (400 ft) 

z 

g loo- V PRI - 550 m/s (1805 ft/s) 

!i 

-BASELINE 

----INVERTER 

70 - 

6o ,1~.1.~1..1..1..1..1..1..( 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(d)llO' &120° 

Figure 26. -(Continued) 
1lOr NPR - 2.1 

1300 

100 - 

-C---SN 

< 90. 

2 / 

z 

z 

d 80- 

. . 

Y BOARDMAN STATIC DATA (30.5m) 

% 

122m SLDELINE (400 ft) 

- 'PRI - 70 70 - 'PRI - 550 m/s (1805 ft/s) 

I I 

- BASELINE 

--- INVERTER 

5 2

8 

& llO140° 

P 

1" 

5: 

0 IOO2 

L 

2 

g go-/ 

2 

z 

k? 80. 0 

70 - 

60- L..~..~..l..I..l..,..I..( 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD ONE-THIRD OCTAVE BAND CENTER FREQUENCY FREQUENCY - Hz 

(e)130°& 140° 

Figure 26. -(Continued) 

88 
NPR - 2.1 

1500 

looN< 90. 

2 

f 

6 so- 

. . 

Y 

T 70- 

G 

f: 

2 60- 

1221~ SIDELINE (400 ftj 

V PRI = 550 m/s (1805 ft/s) 

-BASELINE 

---- INVERTER 

C..!.““‘“‘“,..,..,.,, 

50 100 200 400 800 1600 3150 6300 12600 

1550 

- 

(f) 150° & 155O 

Figure 26. -(Concluded) 

89 

---. ..__ .--.__ __ 
. 0 

11-1 

NE70 - -’ 

z \ ‘\ 

: 

x 60- 

.BOARDMAN STATIC DATA (30.5m) 

. . 

2 

122111 SIDELINE (400 fc) 

VpRI 476 m/s (1560 ft/s) 

q 50 - - BASELINE 

I ---- INVERTER 

ii 

2 

~4O.l~.".'..1..1..l..,,.1,,, 

50 

r5 

100 200 400 800 1600 3150 6300 12600 

: 90 

w r 9o” 

// 

-- 

50 I * * 100 1 I . 200 I . 1 400 I . * 800 I * * 1600 I . . 1 . . I . , , 

3150 

6300 

12600 

ONE-THIFUI OCTAVE BAND CENTER FREQUENCY - HZ 

(a) 60’ & 90’ 

Figure 27.-Comparison of Baseline and lnverter Spectra: NPR = 1.8 

90 
l*r 

NPR - 1.8 

120° 

80 '- 

Ys 

'2 t 

‘\ ‘\. 

\ 

\ ‘\ \ \ 

t 

BOARDnAN STATIC DATA (30.5m) \ 

122~1 SIDELINE (400 ft) . 

d 

V PRI 476 m/s (1560 ft/s) 

-BASELINE 

----INVERTER 

5o 11..1..1 I. II .I .I I.. I . . I. 

50 100 200 400 800 

.‘ 

1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

Figure 27. -(Concluded) 

91 
60 

i 50 

d 

. . 

2 40 

z 

NPR - 1.6 

60" 

BOARDMAN STATIC DATA (30.51~) 

122~1 SIDELINE (400 ft) 

V PRI 416 m/s (1365 ft/s) 

- BASELINE 

----- INVERTER 

,..I~.I..l..l..l..,.,,.., 

50 100 200 400 800 1600 3150 6300 12600 

9o" 

1.‘~~.~..1..1..1..1..1..~ 

50 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a)60°&900 

Figure 28.-Comparison of Baseline and lnverter Spectra: NPR = 1.6 

92 
NPR - 1.6 

mn 70- 

: 

i 60r BOARRUN STATIC DbTA (30.5m) 

122m SIDELINE (400 ft) 

VpRI 416 m/s (1365 ft/s, 

- BASELINE 

---- INVERTER 

5oL 50 Is .I. .I,, ,,.I,.,..,..,,,, 

100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

lb) 120°& 140’ 

Figure 28. -(Concluded) 

93 
60 - 

"E 

2 

z 

BOARDMAN STATIC DATA (30.5m) 

8 50- 122m SIDELINE (400 ft) 

0 

d 

VpRI 344 m/s (1130 ft/s) 

- BASELINE 

. . 

2 

---- INVERTER 

40- 

% 

I 

BO- NPR - 1.4 

60' 

70 - 

3o 5b 1 , . , , . , , , , 

100 200 400 800 

I,.,..,.., 

1600 3150 6300 12600 ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) 90’ 8190’ 

Figure 29.-Comparison of Baseline and lnverter Spectra: NPR = 1.4 

94 
90 NPR - 1.4 

NO0 

z 60 

BOARDHAN STATIC DATA (30.5m) 

. . 122m SIDELINE (400 ft) 

2 VPRI 344 m/s (1130 f&J 

: 50 - - BASELINE 

---- INVERTER I 

ii 

5 4o ,..I ..I. a 1 I 0 1 ..I. .I. *‘*.J 

w 50 loo 200 400 800 1600 3150 6300 12600 

50 

t 

4o lI..l..l..r..‘..,..,..,.., 

56. 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - HZ 

(b) 120’& 140° 

Figure 29. -(Concluded) 

95 
98r OASPL - NPR 2.2 

94 - 

$ goI 

BOARDMAN STATIC DATA (30.5~1) 

649m S/L (2128 ft) 

VPRI - 578 m/s (1895 ft/s) 

+BASRLINE 

--O--1NVERTER .fl 

'A, 

86 - 

82 - 

78 - 

103 

99 

83: 

I 

20 40 60 80 

PNL 

I 

100 120 140 160 

* , d I I 

20 40 60 80 

4 100 120 140 160 

ANGLE REiATIVE TO INLET AXIS - deg 

(a) NPR = 2.2 

Figure 30.-Comparison of Static OASPL and PNL Directivity, Baseline versus lnverter 

96 
g7r OASPL - NPR 2.1 

93 - 

81 - 

77 P 

96 - 

88 - 

84 - 

BOARLMAN STATIC DATA (30.51~) 

649m S/L (2128 ft) 

'PRI - 550 m/8 (la05 ft/s) 

-BASELINE 

--0--1NVERTER 

,o' 

c-0, 

b 

, 1 d I I I 1 I 

20 40 - 60 a0 100 120 140 160 

8o L I 1 271 40 60 80 100 120 140 160 

ANGLE RELATIVE TO INLET AXIS - deg 

(b) NPR = 2.1 

Figure 30. -(Continued) 

97 
a7 

75 

71 

OASPL - NPR 1.8 

. BOARDMAN STATIC DATA (30.510) 

649m S/L (2128 ft) 

'PRI -.476 m/s (1560 ft/s) 

--e-BASELINE 

. --0---INVERTER 

' L 1 I 20 40 60 80 100 120 140 160 

PNL 

74 L I I 1 1 I 

20 40 60 80 100 120 140 160 

ANGLE RELATIVE TO INLET AXIS - deg 

(cl NPR = 1.8 

Figure 30. -(Continued) 

98 
OASPL - NPR 1.6 

84 

72' 

68. 

go86 - 

: 

L 

, a2- 

Fz 

78 - 

74 - 

BOARDMAN STATIC DATA (30.5~1) 

649m S/L (2128 ft) 

'PRI - 416 m/s (1365 ft/* 1 

- .+BBAS!%INE 

--0--1WERTER 

1 ,d, , 

20 40 60 80 

I 

100 120 140 160 

PNL 

P 

/ 

\ / \ 

/’ \ 

/ \ \ 

0 

/ \ 

/ \ 

b 

I 

7o 2k 4b 6i 

I 4 

80 100 120 140 160 

ANGLE RELATIVE TO INLET AXIS - deg 

(d) NPR = 1.6 

Figure 30. -(Continued) 

99 

-- 
OASPL - NPR 1.4 

: “‘s 

' 72- \ 

4 

ti 

d 

h 

‘9 

68 - BOARDHAN STATIC DATA (30.5m) 

649m S/L (2128 ft) 

- 344 m/s (1130 e/s 1 

+BASELINE 

64 - --0--1NVERTER 

6o , 

20 40 60 80 100 120 

1 

140 160 

84- PNL 

80 . 

68 - 

64. 2b 40 60 80 100 120 140 160 1 

ANGLE RELATIVE TO INLET AXIS - deg 

(e) NPR = 1.4 

Figure 30. -(Concluded) 

100 
107. 

102 

AIRCkAFT DISTANCE: 649m (fl28 ft) 

VRWCITY: 91.5ds (!OO ft/s) 

BOARDHAN 30.h DATA WITHOUT 

40 by BOFLICRT EFFECTS : 

&BASELINE 

--O--IWJERTER 

97 - 

82. 

77 - 

'NPR 2.2 

/ 

I I I I 

200 300 400 .I 

500 600 

PRIMARY VELpcITY - VpqT-m/a 

Figure 31.-Comparison of Baseline and lnverter EPNL, Static Levels 

101 

_.-._. -- -_-_-_-_p---- -..-- ~-_-. - ..- -- 
NPR = 2.1 

5o" 

80 1; 

\ 

122m SIDELINE (400 FT) 

vpR1 = 559 m/s (1835 ft/s ) 

-BOAROMAN 3.05 m DATA 

---do by SOTUNNEL-OFF DATA 

l,..l..r..l~.l.,Il.I..l..J 

50 100 200 400 BOO 1600 3150 6300 12600 v) 

4019 ' . " "1 " " 1' '1 ' "1 n '1 'J 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) 50’ & 50° 

Figure 32.-Comparison of Boardman and 40 by 80 Spectra, lnvet-ter Configuration 

102 
NPR = 2.1 

130° 

90 - 

122m SIDELINE (400 FT) 

VpRI - 559 m/s (1835 ft./s) 

-6OARDMAN 3.05 m DATA 

----40 by EOTIJNNEL-OFF DAiA 

s zi 50 1 I 

w" ;o"""*"""" 100 200 400 800 1600 

3150 I 1 6300 , . , 12600 , 

140° 

60L l..l..l,.l..ll.ll.l..\..~ 

50 100 200 400 800 .1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b)130°&1400 

Figure 32.~(Concluded) 

103 

_-----, ,,---,_- ~- - ..-_- --. _______.~_____._.___ -_------ 
108~ NPR - 2.1 - OASPL 

104 

%lOO 

I 

2 

Y 

o 96 

92 

88 

122 m SIDELINE (400 ft) 

VpRI = 559 m/s (1835 ft/s) 

-BOARDMAN 3.05m tiATA 

-- e--40 by gOTUNNEL-OFF DATA 

, 1 

20 40 60 80 100 120 140 160 

PNL 

0 

20 

sl 

40 60 80 100 120 140 160 

FAR FIELD ANGLE RALATIVE TO INLET AXIS - deg 

Figure 33.-Comparison of Boardman and 40 by 80 OASPL and PNL Diractivities, 

lnverter Configuration 

104 
NPR - 2.1 

5o" 

,m,, 

122m SIDELINE (400 ft) \\ 

I * * 1.. 1.. I ..I I .I I. I. I I.. , 

50 100 200 400 800 1600 '3150 6300 12600 

60' 

L... m*aantmal * m1.m I..I 

4o 50 100 200 3150 6300 12600 

ONE-THIRD O&k BAh~“~ENT~:o~kEQ”ENCY - Hz 

(a) 50’ & 60’ 

Figure 34.-Comparison of Tunnel-Off and -On Spectra, lnverter Configuration: NPR = 2. I 

105 

- - 
NPR '8.1 

> 

122m SIDELINE (400 ft) 

SYMBOL TUNNEL 'PRI vI 'R UNITS 

----- OFF 582 23 559 m/s 

1910 75 1835 ft/s 

ON 577 80 497 m/s 

1892 262 1630 ft/s 

60 - 

4o L,...l..l..1..I”‘~~““‘~l 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREOUENCY - Hz 

(b) 70’ 81 80° 

Figure 34. -(Continued) 

106 
NPR = 2.1 

9o" 

122m SIDELINE (400 ft) 

l”11’11.“.1”1”“l’.‘l 

50 100 200 400 800 1600 3150 6300 12600 

6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREOIJENCY - Hz 

Figure 34. -(Continued) 

107 

- 
100 

90 

80 

-NPR = 2.1 

llo" 

-/-\, 

\ 

122m SIDELINE (400 ft) 

.'.".". .""""""I 

100 200 400 800 1600 3150 6300 12600 

(d) 110' &120° 

Figure 34. -(Con tinuedl 

108 
NPR = 2.1 

130° 

122m SIDELINE (400 ft.) 

‘\ 

\ \ \ 

l..‘.““‘.“““.“~‘~‘l 

50 100 200 400 800 1600 3150 6300 12600 

0 

5 llO* 

=: 140° 

80 - 

70 - 

3150 6300 12600 

ONE-THIRD OCTAVE BAND°CEN:E6ROoFREQ"ENCY - Hz 

Figure 34. -(Continued) 

109 
60. 

60 - 

NPR - 2.1 

122m SIDELINE (400 ft) 

I"' * '1 11 1.. 10. I I. 1 I. I I .I 

50 100 200 400 800 1600 3150 6300 12600 

5o Lr..‘..“ll..I..I.~I.~I*l~ 

50 100 200 800 1600 3150 6300 12600 

ONF-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(f) 150°&1550 

Figure 34. -(Concluded) 

110 
NPR = 2.1 

OASPL 

122m SIDELINE (400 ft) 

VR 1 UNITS 

ML I , a L I 

20 40 60 80 100 ,120 140 160 

118- 

106 . 

102 - 

PNL 

98 I irf- 4 

40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - dcg 

(a) 122m Sideline 

Figure 35.-Comparison of Tunnel-Off and -On OASPL and PNL Directivities, lnverter 

Configuration: NPR = 2. I 
NPR = 2.1 

OASPL 

m 88 

-u 

8 

2 

Y 0 84 

80 

457m SIDELINE (1500 ft) 

SYMBOL 1 TUNNEL I VpRI I V.. I VR I UNITS 

582 1 23 I 559 1 m/s 

76L 20 

‘ c 

40 60 80 100 120 140 160 

lD2- 

98 - 

86. 

PNL 

4 

40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(b) 457m Sideline 

Figure 35. -(Continued) 

112 
92- 

88- 

B 84. 

I 

2 

Y 

0 

80 - 

76 - 

'72L 

96’- 

92 - 

80. 

76 - 

NPR - 2.1 

OASPL 

r 649 m SIDELINE (2128 ft) 

<SYMBOL I TUNNEL I VpRI I V, I VR I UNITS 

1 582 1 23 1 559 1 P/6 

I 1892 I 262 I 1630 I ft/s 

I 

20 40 60 80 

, 

100 120 140 160 

PNL 

20 9 40 

FAR 

FIELD6AONGLE 80 4 

RELATIVE TO :i:ET 

120 140 160 

AXIS - deg 

(cl 649m Sideline 

Figure 35. -(Concluded) 

113 
108 

104 

92 ’ 

88b 

r 

NPR = 2.1 OASPL 

I 1935 I 309 I 1626 I ft/s 

8 4 

20 40 60 80 100 120 140 160 

118- PNL 

114- 

8 

$110. 

I 

2 

106 - 

g8 8 

20 60 

8 

40 140 160 

FAR FIELD ANGLE 

R$ATIVE Ti'iNLET A$% 

- deg 

(a) 122m Sideline 

Figure 36.-Comparison of Tunnel-Off and -On OASPL and PNL Directivities, lnverter 

Configuration: NPR = 2.1 

114 
967 NPR - 2.1 OASPL 

92 - 

= 88 - I 

p’ 

2 

0 

84- SYnBOL 1 TUNNEL 1 VpRI 1 VI 1 VR 1 UNITS 

--m-- 1 OFF 1 582 1 23 1 559 1 m/s 

80 - 

: 1 ON 

I 1935 I 309 I 1626 I ftfs 

457m SIDELINE.(1500 ft) 

76 1 I 1 , 

20 40 60 80 100 120 140 160 

PNL 

98 - 

8 

= 94 - 

I 

d 

90 - 

86. 

82L i. .a0 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(b) 457m Sideline 

Figure 36. -(Continued) 

115 
92- NPR - 2;'l OASPL 

88- 

g 84 - 

I 

s 

d BO76 - 

649m SIDELINE (2128 ft) 

SYWJOL 1 TUWm. 1 VpRI 1 Vr 1 VR 1 UNITS 

1 582 1 23 1 559 1 .I/6 

I 1935 I 309 I 1626 I ft/s 

7zL20 , 40 60 80 100 120 140 160 I 

99 PNL 

76 1 # 4 

20 40 

FAR 

FIELD?NGLE RESTIVE TO$LET 120 140 160 

AXIS - deg 

(c) 649m Sideline 

Figure 36. -(Concluded) 

116 
NPR = 2.1 

50 Liz12Zm SIDELINE (400 ft) 

SYMBOL TUNNEL VpRI V.. VR UNITS 

-De-- OFF 582 23 559 m/s 

1910 75 1835 fg/s 

+ ON 577 80 497 m/s 

1892 262 1630 ft/s 

590 94 496 m/s 

63 Hz 

9 20 

4 t 40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(a) 50 Hz 6163 Hz 

Figure 37.-Comparison of Tunnel-Off and -On SPL Directivity, lnverter Configuration: 

NPR =2.1 

117 
NPR - 2.1 

94 

i 

80 Hz 

122m SIDELINE (400 ft) 

’ 

nn 

SY!4EOLlTUNNEL)VpRI ]“I) IVR !mITS A _ 

- I (18921262L16y rr/ 

I - I 11935 1309116Lb 1 KS/S ,’ p/ 

i 82. 

. 0 

. . 

2 

e 78. 

I 

ii :, 

Y 

2 74c 20 c 40 i/a 80 100 120 140 

ii ,,i a d-k 

ii0 

8 

20 

, 

40 /a. 80 100 120 140 160 

FAR FIZD ANGLE RELATIVE TO INLET AXIS - deg 

(b) 80 Hz &I00 Hz 

Figure 37. -(Continued) 

118 
NPR = 2.1 l 

125 Hz 

122m SIDELINE (400 ft) 

+ ON 577 

1892 26211630 ft/s 

& ON 590 

I * I 1 I 

20 40 60 00 100 120 140 160 

160 Hz 

FAR FIELD ANGLE RELATIVE TO INLET AXIS -deg 

M125Hz&15OHz 

Figure 37. -(Con timed) 

119 
98 

94 

90 

NPR = 2.1 

200 HZ 

I 12b SIDELINE (400 ft) 

SYMBOL TUNNEL VpRI VW. VR UNITS fLc‘\ 

' --•-- OFF 

Y 

582 23 559 m/s 

6 

/ 

1910 75 1835 ft/s \ 

& ON 577 80 497 m/s 

1892 262 1630 ftjs 

. + 590 94 496 m/s 

1935 309 1626 ft/s / 

- L 1 

20 40 60 00 100 120 140 160 

250 Hz 

, 

20 

I 

40 6'O 00 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

id) 200 Hz & 250 Hz 

Figure 37. -(Con timed) 

120 
NPR - 2.1 

315 Hz 

122 m SIDELINE (400 Ct) 

t 

20 40 60 80 100 120 140 160 

400 Hz 

a0 

76 t. e l I I . . 

20 40 60 a0 100 i20 

, 

140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS -deg 

(e) 315 Hz & 400 Hz 

Figure 37. -(Continued) 

121 

- 
NPR = 2.1 

500 Hz 

(/d 12210 SIDELINE (400 ft) 

SYMBOL TUNNEL VpRI Ve. VR UNITS 

--e-s OFF 582 23 559 m/s 

1910 75 1835 ft/s 

- ON 577 80 497 m/s 

1892 262 1630 ft/s 

- ON 590 94 496 m/s L 1935 309 1626 ft/s 

, , 

20 40 60 00 100 120 140 160 

- I 4 

20 40 60 00 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS -&g 

(f) 500 Hz & 630 Hz 

Figure 37. -(Continued) 

122 
94 ? 

90 . 

70 - 

740 

NPR = 2.1 

800 Hz 

122m SIDELINE (400 ft) 

SYMBOL TUNNEL VpRI Vm VR UNITS 

--.-- OFF 582 23 559 m/s 

1910 75 1835 ft/s 

-a-- ON 577 80 497 m/s 

1892 262 1630 ft/r 

-o- ON 590 - 94 496 m/s 

1935 309 1626 ft/s \ a 20 40 60 00 100 120 140 160 

I 1 20 40 60 00 loo 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(g) 800 Hz & 1000 Hz 

Figure 37. -(Continued) 

123 
94 - 

90 - 

NPR - 2.1 

1250 Hz 

122 m SIDELINE 

# 4 

20 40 60 80 100 120 140 160 

74 L I 1 

20 40 60 a0 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(h) 1250 Hz & 1500 Hz 

Figure 37. -(Continued) 

124 
NPR = 2.1 

2000 Hz 

r 122m SIDELINE (400 ft) A 

IV; IU'NITSI .I I I 

--o--I OFF 1 582 1 231 5591 m/s 

2?r 

1 1 8 

40 60 80 100 120 140 160 

2500 Hz 

, 20 

0 

40 60 80 loo 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(i) 2000 Hz 812500 Hz 

Figure 37. -(Con timed) 

125 
x 78 

. . 

2 

6 

I 74 

4 

g 70 

In 

: 1220 SIDELINE (400 ft) 

TUNNEL VpRI V.. VR 

0 b-.-m OFF 582 23 559 m/s 

1910 75 1835 ft/s 

& ON 577 80 497 m/s 

1892 262 1630 ft/s 

+ ON 590 94 496 m/s 

1935 309 1626 * I ft/s 4 

20 40 60 80 loo 120 140 -160 

(j) 3150 Hz & 4000 Hz 

Figure 37. -(Con timed) 

126 
86- 

82. 

N 

<78. 

2 

NPR = 2.1 

5000 Hz 

/ 1221~ SIDELINE (400 ft) 

' 

d 

SYMBOL TUNNEL VpRI Vr VR UNITS 

4 -&- OFF 582 23 559 m/s 

1910 75 1835 ft/s 

& ON 577 80 497 m/s 

1892 262 1630 ft/s 

4 ON 590 94 496 m/s 

1935 309 1626 ft/s I 20 40 60 80 100 120 140 160 

-. 1 20 40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(k) 5000 Hz & 6300 Hz 

Figure 37. -(Continued) 

127 

- - 
827 

78. 

74. 

N 

-F 2 

g 70. 

Q 

d 

. . 

3 66. 

s 

I 

ti 5 62 40 60 80 100 I 

62- 

58- 

122m SIDELINE (400 ft) 

SYMBOL TUNNEL VpRI V, VR 

5 20 

582 23 559 m/s 

1910 75 1835 ft/s 

& ON 577 80 497 m/s 

1892 262 1630 ft/s 

+ ON 590 94 496 m/s 

1935 309 1626 ft/s 

I 40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(I) 8000 Hz & 10000 Hz 

Figure 37. -(Concluded) 

128 
OASPL 

(122~) SIDELINE ( 400ft) 

An FROM 15Okn DATA 

On FROM 185kn DATA 

;o 40 60 80 * 100 120 4 

140 160 

16 

I 

PNL 

APNL 

e l2 " - IO Log VPRI.VR 

I 

OL 

i0 40 __. 

CO 80 100 120 140 lb0 

.FAR FIELD ANGLE RELATIVE TO INLET AXIS-- deg 

(a) 122m Sideline 

Figure 38.- Velocity Exponents for OASFL and PNL, lnverter Configuration: NPR = 2.1 

129 
OASPL 

(457m) SIDELINE (15OOft) 

An FROM 150kn DATA 

On FROM 185 kn DATA 

20 L 40 1 60 , 00 I 100 1 1 1 1 

120 140 160 

PNL 

APNL 

n - 10 Log VPRI/VR 

A 20 1 I 1 40 60 I 80 100 120 140 160 

FAR FIELD ANGLE REL.ATIVE TO INLET AXIS- deg 

(b) 457m Sideline 

Figure 38. -(Con tinuedJ 

130 
OASPL 

649m SIDELINE (2128 ft) 

A n FROM 15Okn OATA 

0 ,n FROM 185kn DATA 

L-.- 

20 46 

8 

60‘ 80 100 120 140 160 

16 - 

PNL 

A PNL 

E 12 - 

n = lo Log vpRI/vR 

I 

Iz 

B 

", 8- Y 

i= 

t; 

s 

L2 4- 

2-o 

I 

40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS- deg 

(c) 649m Sideline 

Figure 38. -(Concluded) 

131 
16- 

6491 

Am 

bm 

OASPL 

SIDELINE ( 2128ft) 

FROM 150 kn DATA 

FROM 185kn DATA 

I 1 * I 1 8 1 

20 40 60 80 100 120 140 160 

16- 

PNL 

LOP. (1-h. cos8 ) 

L0g vpRI/vR m m A PNL 

10 Log VPRJVR - 

c 

20 

I I 1 , 1 1 I 

40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

Figure 39.- Velocity Exponents for OASPL and PNL, lnverter Configuration: NPR = 2.1 

132 
NPR = 2.1 

50 nz 

-n FROH 150 L 185kn DATA 

asPL 

" = 10 Log VPRI/VR 

P 

- 

I 

20 40 60 80 100 120 140 160 

L , 

20 40 

FAR FI:D ANGLE kATIVE -%NLET ::kdeg 

140 160 

(a) 50 HZ & 63 HZ 

Figure 40.-Velocity Exponents for SPL, lnverter Configuration: NPR = 2.7 

133 

- 
NPR = 2.1 

80 Hz 

- n FROM 150 I 185kn DATA 

ASPL 

, 

20 40 60 80 100 120 

1 

140 160 

I 

20 40 60 80 100 120 

1 

140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS -deg 

(b) 80 Hz 81100 Hz 

Figure 40. -(Con timed) 

134 
NPR = 2.1 

125 Hz 

20 

1 

40 60 80 100 120 140 160 

2.0 40 60 60 100 120 140 160 4 

FAR FIELD ANGLE RELATIVE TO INLET AXIS -deg 

(c)126 Hz 81160 Hz 

Figure 40. -(Continued) 

135 
NPR = 2.1 

16- 200 Hz 

= 12 - 

I 

5 -n bn FROM FROM 150 150 a & 185h 185kn DATA 

ii ’ ' 

8,. 

n= ASPL 

E 

" = lo Log VPRI/VR lo Log ‘PR#R 

z 

5 

s 

F 4* 

O20 60 40 80 100 120 140 

I 

160 

250 Hz 

40 

FAR FIEL?ANGLE R!!ATIVE TENLET AXlI?hdeg 

140 160 

(d) 200 Hz 81250 Hz 

Figure 40. -(Continued) 

136 
16 

0‘ 

NPR = 2.1 

315 ltr 

- -n .FROM 150 Ii 185 kn DATA 

ASPL 

n=iriTqJq 

20 - -. 4% 60 80 100 120 140 . 

160 

20 

-~ 

FIELDF;\OGLE 

8 

40 REGIVE 100 120 140 160 

FAR TO INLET AXIS- deg 

(e) 315 Hz & 400 Hz 

Figure 40. -(Continued) 

137 
NPR = 2.1 

500 Hz 

n FRMl 150 1 185k11 DATA Q 

c 

20 40 60 80 100 120 140 

.I 

160 

c 

20 40 60 80 120 140 

I 

100 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS-deg 

(f)500 Hz& 630 Hz 

Figure 40. -(Continued) 

138 
NPR - 2.1 

800 Hz 

- n FROH 150 6 185kn DATA 

n = lo ASPL 

Log 'PRI/'R 

1 4 20 40 60 80 100 120 140 160 

1000 Hz 

2-O 40 60 80 100 120 140 160 , 

FAR FIELD ANGLE RELATIVE TO INLET AXIS- deg 

Cg, 800 Hz & 1000 Hz 

Figure 40. -(Con tinued) 

139 
NPR = 2.1 

1250 Hz 

- n FR@l 150 6 185kn DATA 

t I 20 40 60 80 100 120 140 160 

16 1600 Hz 

. 20 8 40 FIELCf\NGLE REFiTIYE 100 120 140 160 

FAR TO INLET AXIS- deg 

(h)1250 Hz&1600 Hz 

140 
NPR = 2.1 

16 

I 

2000 Hz 

;12 - 

,E 

E 

+ n FRCH 150 & 185kn DATA 

y 8. 

E 

2 

> 

4- 

O- 

-- 

20 SO 60 80 100 

, 

120 140 160 

I- 4 

20 ZO 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS- deg 

(i) 2000 Hz & 2500 Hz 

Figure 40. -(Con timed) 

141 
NPN - 2.1 

3150 Hz 

--c- n FROM 150 & 185kn DATA 

n=* 

20 L 40 60 80 

100 120 140 

I 

160 

16- 4000 Hz 

o8 

20 40 60 80 100 120 140 

FAR FIELD ANGLE RELATIVE TO INLET AXIS- deg 

160 

(j)3150 Hz&4000 Hz 

Figure 40. -(Continued) 
NPR = 2.1 

5000 Hz 

16 

I 

: 12. - n FROM 150 & 185 kn DATA 

5 nASPL 

E 

lo Log 'PRI/'R 

E 8- 

, 1 20 40 60 80 100 120 140 160 

16 

I 

6300 Hz 

I 

20 

I 

40 FIEFD 80 100 120 140 160 

FAR ANGLE RELATIVE TO INLET AXIS- deg 

(k) 5OOOHz&63DO Hz 

Figure 40. -(Continued) 

143 
16- 

ONPR = 2.1 

8000 Hz 

- n FROH 150 & 185kn DATA 

2b 

1 

40 60 80 100 120 140 160 

16- 

1ooooHz 

40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS* deg 

(1) 8000 Hz & 10000 Hz 

Figure 40. -(Concluded) 

144 
NH1 - 2.1 

5o" 

16 

n FROM 150 6 185 kn DATA 

A SPL 

" - 10 Log VPRI/VR 

L.. I.. I I I ,,.,,,,,,,,,,,,( 

50 100 200 400 800 1600 3150 6300 12600 

L** I I * I I I 

50. 100 200 400 ,,,,,,,,,,,,,,,J 800 1600 3150 6300 12600 

ONE-TBIRD OCTAVE iAND CENTER FREQUENCY - Hz 

(a) 50° & 50° 

Figure 4 1. - Velocity Exponent versus Frequency, In verter Configuration: NPR = 2.1 

145 
NpR - 2.1 

9o” 

16 - 

ct- n FROM 150 6 185kn DATA 

= 

12 

- A SPL 

” 

- 

1 10 Log VPRI/VR 

ii 

k 

s 8- 

5 

5 

!s 4- 

l d a 

00-e- - 

oL.‘l’.“““‘.“““.“ll 50 100 200 400 800 1600 315b 6300 12600 

16- loo0 

Ol.‘l’l”““““““““l 

50 Too 100 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b)90° &loo0 

Figure 4 1. -(Con tinuedl 
NPR - 2.1 

130" 

16 

I 

_O_ II FROM 150 6 185 kn 

" - 10 Log 0 VPRI/VR SPL 

DATA 

I I I I, I I I, I I I I, I,, I, I I I I, ’ 

50 100 260 400 800 1600 3150 6300 12600 

l..l~llllll.lllll.~lllll, 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

k)130° & 1400 

Figure 4 1. -(Concluded) 

147 
80 

70 

60 

50 

40 

30 

9c 

80 

70 

60 

50 

40 

12213 SIDELINE (400 ft) 

]SYMBOL 1 TUNNEL 1 .VpRI 1 k I 

1 --- I I I 1 

VR 

OFF 494 19 475 I 'm/s I 

1 1620 1 64 I 1556 

I I I 

I ft/s ; 

ON I 482 I 80 I 402 1 m/s I 

1 1583 1 262 1 1321 

I I I 

I..l..l..r..l..l..‘..~~~I 

50 100 290 400 800 1600 3150 6300 12600 

7o" 

,* 

I * . 1 ..I. I 1. .I m 1 1.. 1.. 1. * I 

56 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) 50° & 70° 

figure 42.-Comparison of Tunnel-Off and -On Spectra, lnverter Configuration: NPR = 1.8 

u 

148 
90 

80 

70 

60 

50 

40 

40 NPR - 1.8 

70 

ISiMBoL I TUNNEL I VPRI 1 VW I v. 

i A 

1 UNITS 

1 I 1 I I 

I 

--- OFF 494 19 I 475 I m/s 

60 I 1 1620 1 64 I 1556 

I I I 

I ft/s 

I I 1 1583 42I 1 262 801 1321 4021 m/s 

I I I I 

I ft/s 

50 

80 

I 

~..1..‘..1..1..1..1..1..1 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b) 90’ 81 100° 

Figure 42. -(Continued) 

149 

II 1-.1#111 .-1-.11-1.---. II..---... ,.. . , . _ . . . . . . . . . -- .-. ..-. .-- 
loo9t 3- 

8( I7( ) - 

6( 1 - 

5( IL 90 

60 

50 

40 

NPR - 1.8 

1100 

[SYMBOL 1 TUNNEL ( ( k I 1 UNITS 1 

1 --- 1 OFF I VpRI 494 I 19 1 I VR 475 I dS I 

I 1 1620 I 64 1 1556 1 

I I I 

ft/s 1 

I ON 1 I 1583 42I 1 262 80 I ( 1321 4021 m/s I 

1 I I I 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

Figure 42. -(Con timed) 

150 
I NPR - 1.8 

130° 

80 - 

60 - 

so100 

80 

60 

50 

lSYMBOL I TUNNEL I VpRI I 

I 

v- I VR 

OFF I 494 I 19 1 475 1 m/s I 

I I ( 1620 I 64 1 1556 I I I ftjs I I 

iI I I I I 

ON I 482 I 80 1 402 1 m/s I 

1 1583 1 262 1 1321 

I I I I / ft/s i 

I I I I I I I 

LM I , I , . , . . , , , , . . , , , , 

50 100 200.. 400 800 1600 3150 6300 12600 

F 

140° 

1. .I..r..,,,,,.,..,,;,~~( 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(d) 130°& 14oo 

Figure 42. -(Con timed) 

151 

- -- 
122m SIDELINE (400 ft) 

N 

I 

0” 

Q d 

loo80 - 

70 - 

60- 

80- 

60 * 

50- 

IsmL 1 TUNNEL I V,,, I 

rnL 

VI 1 1 ‘R 1 UNITi I 

I 

I 494 I 19 1 475 ~~~-~ .I m/s 

I 

t 

I 1620 I 64 I 1556 

I I I I 

I 80 I 402 I n/s I 

1 1321 1 ft/s I 

I--- I 

NPR - 1.8 \ ‘.\\ 

150° ‘. 

\ 

‘\ 

-. \ \ \ 1 --\ \ 

1..1..‘..1*.1.~11.1.1~ 1 

50 100 200 400 800 1600 3150 6300 12600 

15s” 

\ \ \ 

“\, -1 \ \ 

Il.1 *.‘a a I I I l..l..l. 

50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(e) 150° &155O 

Figure 42. -(Concluded) 

152 
86- 

82 - 

70 - 

NPR - 1.8 

649 m SIDELINE (2128 ft) 

SYMBOL TUNNEL "PRI "- "R UNITS 

---Q-- OFF 494 19 475 m/s 

1620 64 1556 ft/s 

66L 

irp- & i. 

-. .- , 

80 100 120 140 160 

92 

88 

76 

72 

PNL 

4 

-. -.-.- _- ~~~ 20 40 

FAR 

FIELD6'MGLE REfiTWE TO%LET 120 140 160 

AXIS - deg 

(a) 100 kn 

Figure 43.-Comparison of Tunnel-Off and -On OASPL and PNL Directivities, lnverter 

Configuration: NPR r 1.8 

153 

I -- 
UNITS I 

70 - mls I 

ft/s I 

116 I 

1 1583 1 262 J 1321) ft/s 1 

66 8 20 40 60 80 I 

100 120 140 160 

92- 

88 - 

76 - 

l2 I, 20 4 40 60 80 100 120 140 160 

FAR PI!?LD ANGLE RELATIVE TO INLET AXIS -deg 

(b) 150 kn 

Figure 43. -(Concluded) 

154 
16- 

0 

16 

5 12 

I 

OASPL 

649 m SIDELINE (2128 ft) 0 

o n FROH 1OOkn DATA 

A n FROM 150kn 

I 4 

20 40 60 80 100 120 140 160 

PNL 

n= 

, 

20 

4 

40 F!:LD 80 100 120 140 160 

FAR ANGLE RELATIVE TO INLET AXIS-W 

Figure 44.-Velocity Exponents for OASPL and PNL, lnverter Configuration: NPR = 1.8 

155 
OASPL 

649 m SIDELINE ( 2128 f t) 

A P FROn 15Okn DATA 

0 m FRCM 1OOkn DATA 

I I 

20 40 60 80 

I 

100 120 140 160 

PNL 

APNL 

m - IO Log VPRI/VR - 

LOR ( l-Hop c“sg ) 

Log VPRI/VR 

# 

20 

1 1 4 

40 60 80 100 120 140 160 

FAR FInD ANGLE RELATIVE TO INLET AXIS- deg. 

Figure 45.- Velocity Exponents for OASPL and PNL, lnverter Configuration: NPR = 1.8 

156 
NPR - 1.6 

SO0 

60. 

I 122~ SIDELINE (400 ft) 

SYMBOL ! TUNNEL 1 VpRI 1 Ve 1 VR 1 UNITS I 

I I I I I I 

------ I OFF 1 436 1 17 ( 419 I m/s I 

I 1430 I 55 11375 1 ft/s I 

-I ON 1 423 1 80 I 343 1 m/s I 

1 1389 1 262 11127 I ft/s I 

60. 

soLL"l"'..'1.1'.1IIl."..l 4o 50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) 50° & 70’ 

Figure 46.-Comparison of Tunnel-Off and -On Spectra, lnverter Configuration: NPR = 1.6 

157 
NPR - 1.6 

110° 

122111 SIDELINE (400 ft) 

60. SYMBOL I TDNNEL I VpRI I VI I VR I UNITS I 

I I I I I I 

----- 1 OFF 1 436 I 17 1 419 I m/s I 

I 1 1430 I 55 11375 I ft/s I 

so- -l ON 1 423 I 80 I 343 I m/s I 

1 1389 I 262 Ill27 I ftfs I 

4o 55 1..1..1..1.,1..1..1..1 

100 200 400 0 1600 3150 6300 12600 

60- 

50- 

600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b) IlOo& 120’ 

Figure 46. -(Continued) 

158 
SYHBOL I TUNNEL I VpRI I VI I VR I UNITS ) 

I I I I I 

__---- I OFF 1 436 1 17 1 419 I m/s I 

1 1430 1 55 11375 I ft/s I 

1 ON 1 423 1 80 1 343 1 m/s 1 

I 1 1389 1 262 I1127 1 ft/s I 

4oL 50 I..'..'" 1..t..1*.1..1..l 100 ,400 800 1600 3150 6300 12600 

go60. 

40-5i) J ..,.,,..,..,..,..,,,,.,J loo 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

Figure 46.-(Concluded) 

159 
82 

1 

NPR = 1.6 

OASPL 

1 

,~ 

a 1 , 

40 60 80 100 120 140 160 

PNL 

84 - 

72 - 

68- I , 

20 40 2 

FAR FIEL6DOANGLE RELATIVE TJ’FNLET AXiS’- deg 

140 160 

Figure 47.-Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

lnverter Configuration: NPR = 1.6 

160 
OASPL 

16 

i 

649 m SIDELINE (2128 ft) 

A n FROM 150kn DATA 

. 

I 8 

20 40 60 80 100 120 140 160 

=12 

' t 

APNL 

" = lo Log VPRI/VR 

PNL 

- 1 I 

, 

20 

1 

40 F*ELDYNGLE 80 100 120 140 160 

FAR RELATIVE ~0 INLET AXIS -- deg 

Figure 48.-Velocity Exponents for OASPL and PNL, lnverter Configuration: NPR = 1.6 

161 
OASPL 

16- 

OSIDELINE (2128 ft) 

FROU 150kn DATA 

8 I I I 

20 40 60 80 100 120 140 160 

PNL 

mm APNL LOP, (~-MC., case ) 

10 Log VPRI VR - Log VPRI/VR 

, 

20 

J 

40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS- deg. 

Figure 49.-Velocity Exponents for OASPL and PNL, lnverter Configuration: NPR = 1.6 

162 
76- 

72 - 

60 - 

NPR = 1.4 

649 m SIDELINE (2128 ft) 

56L20- ~--- 

I 

40 60 80 100 120 140 160 

82r 

66 

t 62L2~-*o - ~--- Q. 86 100 120 140 160 4 

FAR FIELD ANGLE RELATIVE TO INLET AXIS -- deg 

Figure 50.-Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

lnverter Configuration: NPR = 1.4 

. 

163 
649m SIDELINE (2128 ft) 

95- 

-e- BoARDMAN 30.5m OASPL 

A BOARDMAN 30.5m PNL 

90- 

0 40 by BOiUNNEL OFF 

m 40 by 80 loo kn 

A 40 by 80150 kn 

# 40 by 80 185 kn 

eF - 5o” 

V 

NPR 

--&--' 4 2.1 

- 2.1 

2.0 

-c- / 

200 500 660 

PRIMARY RELATIVE JE - vc )- m/r 

(a) 50’ 

Figure 51.-Tunnel-Off and -On OASPL and PNL versus Primary Velocity, lnverter Configuration 
649m SIDELINE (21281 ft) 

-e- BOARDNAN 30.% OASPL 

--~-BOARCHAN 30.3~ PNL 

. 40 by BOTUNNEL OFF 

l 40 by 80 100 kn 

A 40 by 80 150 kn 

4 40 by 80 185 kn 

l o 

/ 

/ -.. l&R - 2.2 

d 

,-J-N’ 2.1’ / 

/ 

1.9” 2.0 ! 

200 do 400 500 

PRIMARY RELATIVE JIjT VELOCITY (VP& - V, ) cy m/c 

(b) 60’ 

Figure 5 1. -(Continued) 

j 

I 

I 

I 

660 
1051 

loo 

95 

85 

649m SIDELINE (2128 ft) 

-e- BOARDMAN 30.5m OASPL 

see--. BOARMAN 30.5~1 PNL 

0 40 by BOTUNNEL OFF 

l 40 by 80 100 kn 

A 40 by 80 150 kn 

t 40 by 80185 kn 

200 

BP = 7o” 

P 

1.5 

--o 

P 

1.4 

600 

PRIMARY RELATIVE JE vELoCITP (vpRi - VI )‘” n/S 

J 

785 

-80 

- ?5 

B 

- 70.2 

2 

3 

- 65 

- 60 

- 55 

Figure 51.~(Continued) 
100 649m SIDELINE (2128 ft) 

-@- BOAFIDNAN 30.5m OASPL 

- BOARMAN 30.h PNL 

95- 

2 

t 

t gob? 

. 40 by BOTUNNEL OFF 

l 40byBOlOOkn 

A 40 by 80150 k,, 

t 40 by 80185 kn 

85- 

80 - 

75- 

% = 80' 

200 500 600 

- Vcu )'u m/S 

-85 

-80 

-75 

-65 

-60 

-55 

(d) 80’ 

Figure 51.~(Continued 
H 

649m SIDELINE (2128 ft) 

-o- BOARDHAN 3D.h OASPL 

A BOARDMAN 3D.5m PNL 

0 40 by 80TuNNEL OFF 

l 40 by 80100 kn 

A 40 by 80 150 kn 

95 

t 

t 40 by 80185 kn 

% 

& 

I god 

85- 

BO75- 

8, * 9o" 

/ 

1.5 

----a 

P 

1.4 

d 1.3 

200 400 500 600 

PRIMARY RELATIVE JET VELOCITY (VpRI - v, )-w m/s 

-85 

-Ml 

-75 

-60 

-55 

(e) 90’ 

Figure 5 1. -(Continued) 
110 - 

1, 

105 - 

loo649m SlbFiLINE (2128 ft) 

-6- BOARDNAN 30.5m OASPL 

‘1 $dW 3b.5m PNL 

6 40 by 80TUNNRL OFF 

a 40 by 80 100 kn 

A 40 by 00150 kn 

t 40 by 80 185 kn 

BF - loo0 

,J/- p-c 

,, J u’ /r / /’ 

c’ de ,x0* f 

61 

/ -. /J/ 2.0 ,.$ 

;Y ;J 6 1.9: 

- 2*2 

+” l.ie 

‘,/’ 

-i 1.7 j 

‘-a260 3bo J 1.4 460 560 600 

PRIFURY RELATIVd JE VELDCI’I*I dVpR, - Vm )&ids 

1.3 

(f) loo0 

Figure 5 1. -(Continued) 

70 

65 

60 
z 

0 

649m SIDELINE (2128 ft) 

-O- BOMLMAN 30.5m OASPL 

BOARLMAN 30.5~1 PNL 

40 by EOTUNNEL OFF 

40 by 80100 kn 

40 by 80150 kn 

40 by 80185 kn 

'F - 110" 

200 

PRIMARY RElATiVE JET 

400 5QO 600 

-vq )-m/s. 

-9 0 

-e 5 

-8 0. 

-7 

- 6! 

Figure 51.~(Continued) 
11 

Y 

104. 849m SIDELINE (1128 ft) 

I -8- BOARDUAN 30.5m OASPL 

I _O_ BOARDMAN 30.5m PNL 

100 

l 40 by 80TIINNEL OFF 

I 40 by 80 100 kn 

A 40 by 8D190 kn 

90 

t 

85 - 

80- 

4 40 by 80185 kn 

8, - l2O0 

200 300 4tio SbO 

Pr(II3ARY RELATtVC JET VIiLOCITY, (&, - p., ) hr fls 

(hI120' 

Figure 51.~(Continued) 

.., 

/ 

i ‘. 

I. !. 

i 

I 

I : 

I 

1 
10 

‘[ 

loo95 - 

6491~ SIDELINE (2128 ft) 

-e- BoARDl4AN 30.h OASPL 

.*- BOARUHAN 30. Sm PNL 

. 40 by 8OTUNN!tL OFF 

l 40 by 80 100 kn 

A 40 by 80 150 kn 

( 40 by 80 185 kn 

266 

PRIMARY 

OF - 130° 

: 9, 

./ 

1.7 7 1.6 

580 6dO 

JtT VFaLOCtTY (vpdI - 0” ) Q m/S 

- 2.2 

[i) 130' 

Figure 5 7. - (Con tinuedl 
649m SXDELINE (2128 ft) 

-e- BOABtMAN 30.h OASPL 

_e_ BOARMAN 30.5m PNL 

0 40 by 80 TbNEL OFF 

m 40 by 80 #JO kn ' 

A 40 by 80 hi0 kn 

4 40 by 80 1$5kn 

I 

200 

pRItbRY RElATIti 

Figure 5 1. -(Continued) 

6iO 

! 

/ 

i 

I 

/ 

( 

I 
g 

E 

2 65 

d 

aa 

75 

70 

.649a GIDELINE. (2128 it, 

-Q- BOABDHAN 30:5m/ OASPL 

+ BOARDHAN 30. sm: PNL 

0 40 by 80TUNNEZLi OFF 

n 40 by 80100 kn 

A 40 by 80150 kn 

b 40 by 80185 kn 

240 

/ 

' - 1500 : l@F 

I 

I 

A 

i 

0 

/ 

4&l 500 6hO 

PRIMARt RELATIVd JET VEMCITY tVVpRr - v.m I- m/S 

/ 

(k) 150' 

Figure 51.~(Continued) 
95 . 

90. 

85.. 

70 

65- 

‘% - 159 

649m SIDELINE (2128 ft) 

-e- BDARDMAN 30.5m OASPL 

-(t- ROARRUN 3o.zn PNL 

0 40 by 80 TUNNEfL OFF 

l 40 by a0 100 Ln 

A 40 by 80 150 kn 

b 40 by 80 185 kn 

200 600 

PRIMARY RELATIVE JET LCCITY (VpRI - V, )- n#s 

1 

-85 

-eo 

- 65 

-60 

Figure 51.~(Concluded) 
AIRCRAFT DISTANCE: 649 m (2128 ft) 

VELOCITY: 91.5 III/S (300 ft/s) 

BOARDMAN 30.5 m DATA 

+EPNL UITH~UT FLIGHT EFFECT 

PLOTTED VERSUS VPRI 

--0--EPNL k1T~40 by ~~FLIGHT ; 

EFFECTS PLOTTED VERSUS (VpkI - V,) 

260 

L I 

0 

PRIMARY V:L&ITY - VpRI 04io(VpRI 

500 600 

- vr ) - m/s 

. 

2.2 

Figure 52. -Static and Es tima ted Flight EPN L Characteristics, In verter Con figuration 

176 
98- 

94- 

02 - 

92- 

88 - 

76 - 

72- 

SIDELINE - 649 P (2128 ft) 

“PRI - 578 m/S (1895 ft/sJ 

BASELINE 

------ INYERTER 

STATIC 

2b 40 I 60 I 80 I I 120 I I I 

100 140 160 

FAR FIELD ANGLE RHATIVE TO INLET AXIS -deg 

Figure 53.-Comparison of Static and Flight OASPL Directivity for Baseline and lnverter 

177 
102- STATIC 

SIDELINE - 649m (2128 ft) 

'PRI - 578 &(I895 ft/S) ' 

98 - 

-BASELINE 

-----1NVERTER 

06- 

a2 , 1 

20 40 60 80 100 

, 

120 140 160 

96 

r 

FLIGHT 

92 - 

m aaE 

d84. 

80 

t 

76 1 2b 1 40 60 80 100 140 I 

120 160 

FAR FIELD ANGLE RESTIVE TO INLET AXIS -deg 

Figure 54.-Comparison of Static and Flight PNL Directivity for Baseline and lnverter 

178 
AIBCEAFI DISTANCE: 64bm (2128 ft) 

VELOCITY: 91.5m/8 (300 ft/s).. 

BOARIXAN 30.5~ DATA WSCH 

40 by BOFLICHT EFFECT6 

__t_ BASELINE 

97 ---o---I~~RTER 

1 

200 

I I I I 

300 400 500 600 

PRIMARY VELOCITY - VFRIwm/s 

Figure 55.-Comparison of Baseline and lnverter EPNL, Flight Levels 

179 
94- 

go78- 

NFB - 2.1 

OASPL 

74L 1 1 I 1 I 1 I 100 I 20 40 60 80 120 140 160 

649m SIDELINE (2128 ft) 

SYMBOL JTDNNELI VPRI 1 VI 1 VR IUNITS 

98 PNL 

lgL I 1 1 1 1 I 1 I 20 40 60 I30 100 120 140 160 

FAR FIELD ANGLE REIATIVE TO INLET AXIS - deg 

(a) NPR = 2.1 

Figure 56.-Comparison of Tunnel-Off and -On OASPL and PNL Dhctivities, Internal 

Mixer Configuration 

180 
NPR - 1.8 

OASPL 

g2r PNL 

649m SIDELINE (2128 ft) 

\ 

76 

72 1 2’0 1 I I I I I I 

40 60 80 100 120 140 160 

FAR PIFLD ANGLE RELATIVE TO INLET AXIS -d=S 

(b) NPR = 1.8 

Figure 56. - (ConcludedJ 

181 
16 r 

649m SIDELINE (2128 ft) 

A n FROM 150kn DATA 

n FROM 185kn DATA 

c l2 

0 

I 

OASPL 

, I 

20 80 40 60 100 120 140 160 

A PNL 

10 m3 VPRI/VR 

PNL 

I 

20 

I I I 1 I 1 3 

40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS-- +?Z 

(a) NPR = 2.1 

Figure 57.-Velocity Exponents for OASPL and PNL, Internal Mixer Configuration 

182 
16 OASPL 

649m SIDELINE (2128 ft) 

A II FROM 15Okn DATA 

L 

20 

I I L I 1 I I 

40 60 80 100 120 140 160 

16 

A PNL 

n- 10 Log VPRI/VR 

PNL 

i 

20 

I I 1 I I I 1 

40 60 80 100 120 140 160 

FAR FIELD ANnE RELATIVE To INLET AxIs- deg 

(b) NPR = 1.8 

Figure 57. - (Concludebl 

183 
107 

102 I 

97 

4 

s 

I 

92 

87 

82 

77 

AIRCRAFT DISTANCE: 649m (2128 ft) 

VELOCITY: 91.5 m/s (300 ft/S) 

BOARSUAN 30.5~ DATA 

EPUL UITMOLJT FLIGHT EFFdCT 

PLOTTED VERSUS VpRI 

---O--- EPUL WITH 40 by 80iLICHt 

EFlECTS PLWED VERSUS CVmII - V- ) 

, 1 1 I 

200 3ocl 400 500 600 

PRIMARY VELOCITY - VpRI OR CVpRI - V, )- m/,s 

Figure 58. -Static and Estimated Flight EPNL Characteristics, Internal Mixer Configuration 

184 
90 STATIC 

SIDELINE - 64% (2128 ft) 

"PRI - 578 m/s (1895 ft/s) 

94 -BASELINE 

-----1NVRRTER 

--I~ERNALIUXER 

82- 

I 1 I I I I I I I 

20 40 60 80 100 120 140 160 

92- 

88- 

76- 

FLIGHT 

I I I I 100 120 140 160 

FAR FIELD mcLE ItSmTIvE To INLEr - deg 

Figure 59. -Comparison of Static and Flight OASPL Directivity for Baseline, lnverter, 

and Internal Mixer 

185 
102r 

98 - 

23 

94 - 

& I 

2 

go86- 

STATIC 

SIDRLINE - 649m (2128 ft) 

"PRI - 578 m/s (1895 ft/sJ 

-BASELINE BASELINE 

-----1NVERTER 

--INTERNAL MIXER 

82 LA I I 1 I 1 I I 20 40 60 80 100 120 140 160 

96t FLIGHT 

92- 

88- 

?I 

t 

I 

2 84- 

Vr - 91. 

80 76t , 1 1 i. l;o ' ' ' 20 40 60 120 140 160 

FAR FIELD ANGLE RELATIVE To INLET - deg 

Figure 60.-Comparison of Static and Flight PNL Directivity for Baseline, lnverter, and 

Internal Mixer 

186 
107- 

102;. 

97 . 

82:. 

77’ 

AIRCRAFT DISTANCE: 649m (2128 ft) 

VELOCITY: 91.5 m/s (300 ftls) 

KMUMAN 30.5111 DATA WITHOUT 

FLIGHT EFFECT 

-e- BASELINE (JT8D-17R) 

mm A-- INTERNAL MIXER (JTBD-17) 

-- 8 -- INVERTER (JTBD-17R) 

, 

200 300 400 500 

PRIMARY VELOCITY - VpRI-m/S 

4 

600 

Figure 61.-Comparison of Baseline, lnverter and Internal Mixer EPNL, Static Levels 

187 

-- 
107. 

1 

102 

97 ' 

z 92. - 

5 

1 

rl 

E 

w 

87.. 

82 - 

77- 

AIRCRAFT DISTANCE: 6491 (2128 ft) 

- VELOCITY: 91.5m/s (300 ft/s) 

BOARDMAR 30.510 DATA WITH 

40 by 8OFLICHT EFFECTS 

-BASELINE (JTBD-17R) 

--A-- INTERNAL MIXER (JTBD-17) 

. -- @- INVERTEk (JTBD-17R) 

t 4 

200 300 400 500 600 

PRIMARY VELOCITY - V.pRI*m/s 

Figure 62.-Comparison of Baseline, lnverter and Internal Mixer EPNL, Flight Levels 

188 
90 

80 

70 

Ne 

1 

i 60 

d 

ii s50 

I 

NPR - 2.2 

60: 

BOARDMAN STATIC DATA (30.51~) 

122m SIDELINE (400 ft) 

V PRI 578 m/s (1895 ft/S) 

- BASELINE 

---- INVERTER/PLUC 

9o" 

60 

50 '50 1. * 100 1 * * 1. * 400 ‘* ‘1 800 ‘. 1600 1 * . 3150 1 -a 6300 ’ a * 12600 I 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

Figure 63.-Comparison of Baseline and lnvwter/Plug Spectra 

189 
NPR - 2.2 

120° 

100 - 

hlE 

> 90. 

2 

0 

zl 

. 

o 80- 

B 

2 

I 70 - 

ii 

P rl 

bOBOARDMAN STATIC DATA (30.5d 

122m SIDELINE (400 ft) 

VpRI 578 m/s (1895 ft/S) 

-BASELINE 

---- INVERTER/PLUC 

-- INVERTER 

I. - 1’. ” * “‘I. - 1’ ‘1 * ““1 50 100 200 400 800 1600 3150 6300 12600 

140° 

I * ’ ’ ’ * ’ . ’ ’ * * ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ 

50 100 200 0 1600 3150 63 loo’ 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

Figure 64.-Comparison of Baseline and lnverter/Plug and lnverter Spectra 

190 
OASPL-NPR 2.2 

BOARDHAN STATIC DATA (30.510) 

649m s/L (2128 ft) 

VpRI '. 578 m/s (1895 ft/s) 

-O-- RELINE 

--o-- INvnTmt/PLuc 

-A- INWRTER 

93 

89 

e I 

2 

% 85 

81 

77 

101 

97 

/ 

20 , 40 60 80 100 120 140 160 , 

PNL 

85 - 

40 " 60 

, 

80 100 120 140 160 

ANGLE RBLATIVB TO INLET AXIS- deg 

Figure 65.-Comparison of Static OASPL and PNL Directivity, Baseline versus lnverter/Plug 

and lnverter 

191 
NPR - 2.1 

60° 

122m SIDELINE (400 ft) 

60- 

soSYMBOL 1 TUNNEL 1 VpRI I Vr I 1 UNITS 

I I , I 

VR 

I 

1 

----- 1 OFF I 584 I 23 I 561 I m/s I 

I 1 1916 1 75 I 1841 I ft/s f 

I ON 1 562 I 95 1 467 I m/s 1 

l 1843 1 310 1 1533 1 ft/s 1 

4oL 5'0 

1 . . I . . I , . I , . I , . I , , , , , , 

100 200 400 800 1600 3150 6300 12600 

99 

60- 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) 80O & 8o” 

Figure 66.-Comparison of Tunnel-Off and -On Spectra, lnverter/Plug Configuration 

192 
NPR - 2.1 

loo0 

N I 1221~ SIDELINE (400.ft) \ 

q 

z 70 

2 

g 

----- 

d 

60 

ii 

: 

I 

ti 

.8~ . I I . .3i50' . I . . , 

0 1600 6300 12600 

z rl 100 

120° 

50L5b 

,..~..~..,..,,.,..,..,.., 

100 '200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAN'0 CENTER FREQUENCY - Hz 

lb) 100’ & 120’ 

Figure 66. -(Continued) 

193 
--m-e60 

50 I I * .lo' . I I I I I '8Ao' , , , , , , , , , , , 

50 200 400 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

M140°& 1500 

Figure 66. -(Concluded) 

194 
92r 

aa76. 

72- 

96- PNL 

92- 

% aaf 

I 

J 

t 

04- 

aoI 

20 40 

NPR - 2.1 

OASPL 

64% SIDELINE (2128 ft) 

VR 

I UN1TS I 

---Q--- 561 I m/s 1 

ia41 I ft/s I 

491 I m/S I 

1612 I ft/s I 

-I CZ I 562 I 95 I 467 I m/s I 

V I i la43 I 310 I 1533 i ftis i 

a0 

, 

60 100 120 140 160 

76 1, I 1 I I I 1 t 

20 40 60 a0 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

(a) NPR = 2.1 

Figure 67.-Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter/Plug Configuration 

195 
86. NPR - 1.8 

OASPL 

2 7aI 

2 

2 64% SIDELINE (2128 ft) 

O 74- I 91’ SYMBOL ITUNNELIV,,,IVm 

I I I 

I VR IUNITS 

I I I 

70- / 

J’ ---@--- I OFF 1 497 I 19 I 478 I m/6- I 

1 1632 I 64 I 1568 I ft/j 1 

--o--l ON 1 492 I 56 I 436 I m/s I 

I 1614 I la3 I 1431 I ft/s 1 

-Y+; ON 1 1583 42I 1 267 a1I 1 1316 401 1 ft/s m/S 1 I 

66 2!0 I 1 

40 60 a0 100 120 140 

4 

160 

90r PNL 

86- 

Q azt 

I 

E 

7a74. 

7o b 20 , 40 I 60 80 1 100 1 1 I , 

120 140 160 

FAR FIELD ANCLE RELATIVE TO INLET AXIS - deg 

(b) NPR = 1.8 

Figure 67. -(Concluded} 

196 
IL- 

: 12- 

E 

P 

& 

Z ac 

G 

g 4- 

16 

OASPL 

649 m SIDELINE (2128 ft) 

A n FROM 150 kn DATA 

0 n FROl4 la5 kn DATA 

26 1 40 60 

a0 100 120 

1 

140 160 

PNL 

n- A PNL 

10 Log VpRI/VR 

20 I 40 I 60 a0 I I loo 120 , 

140 160 

FAR FIELD ANGLE RELATIVE TO INLEI AXIS-deg 

(a) NPR = 2.1 

Figure 68.-Velocity Exponents for OASPL and PNL, lnverter/Plug Configuration 

197 
16. 

c 12- 649 m SIDELINE (2128 ft) 

I 

OASPL 

I I I 1 

20 40 60 80 100 li0 ll0 lA0 

16 

0' 

PNL 

" - 

APNL 

10 Log VPRI/VR 

L 

20 

I I I 1 1 I 

40 60 80 100 120 

I 

140 160 

FAR FI!ZLD ANGLE RELATIVE TO INLET AXIS-&g 

(b) NPR = 1.8 

Figure 68. -(Concluded} 

198 
eF - 6d" 

64910 SIDELINE (2128 ft) 

-QJ- BOARDMAN 30.51~ OASPL 

. G BOARMAN 30.51~ PNL 

0 40 by a0TURNEL OFF 

I 40 by 80100 kn 

A 40 by 80150 kn 

# 40 by 80185 kn 

200 300 400 500 600 

PRIMARY RELATIVE JET VELOCITY (VpRl - Vc )w m/s 

(a) 60' 

Figure 69.-Tunnel-Off and -On OASPL and PNL versus Primary Velocity, lnverter/Plug Configuration 
105 

100 

95, 

z 

90. 

L 

i 

85. 

80 

75 

BF - LOO0 

649m SIDELINE (2128 ft) 

--6- BOABDW 3U.5m OASPL 

- BOARDMAN 30.5m PNL 

: 40 by 

by 

SOTU~WEL 80 OFF 

100 kn 

A 40 by 80 150 kn 

4 40 by 80 185 kn 

200 300 400 500 600 

PRIMARY RELATIVE JET VELOCITY (VpRr - Va )- mjs 

(b) 100° 

Figure 69. -(Con timed) 
DS 

[ 

oo95- 

30. 

85 - 

80- 

75- 

200 

PRIMARY 

$ = 140° 

649n SIDELINE (2128 ft) 

-Q- BOARLMAN 30.5m OASPL 

-IlOARcFIAN 30.5m PNL 

0 40 by 80 TIR(NEL OFF 

I 40 by 80 100 kn 

f 40 by 80 80150 185 kn 

RELATIVE JE 

400 500 660 

v-,-m/s 

Figure 69. -(Concluded) 

,195 

j90 
107- 

102 

97 

z 2 92 

I 

cl 

z 

87 - 

82 - 

776 

AIRCRAFT DISTANCE: 649m (2128 ft) 

VELOCITY: 91.5 m/s (300 ft/S) 

BOARDMAN 30.5 m DATA 

d EPNI. wITHOUI FLIGHT EFFECT 

PLOTTED VERSUS VpRI 

----O---- EPNL WITH40 by 80FLfCHT EFFECTS 

PLOTTED VERSUS (VP,, - V,) 

I 

, 

200 500 600 

PRIMARY VELOCITY - VpRI OR (VpRI - Vlohds 

Figure 70. -Static and Es tima ted Flight EPNL Characteris tics, lnverter/Plug Configuration 

202 
NE 

BOARMAN STATIC DATA (30.5m) 

: 

122m SIDELINE (400 ft) 

V PRT 578 m/s (1895 R/s) 

2 60. 

Q 

-BASELINE 

d 

- -INVERTER/MIXER 

------INV./MIXER/SHIELD 

60 

t 

5oL 5”o 

I, *,,,I,,,..,..,..,.., 

100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) 6o” & 9o” 

Figure 71.-Comparison of Baseline; lnverter/Mixer with and without Shield Spectra 

203 
110 NPR - 2.2 

120° 

1lOr 

60. 

BOARmAN STATIC DATA (30.5m) 

122m SIDELINE (400 ft) 

VPRI 578 m/s (1895 ft/s) 

- BASELINE 

-- INVERTER/KtXER 

----- INV./WIXER/SHIELD 

I * * ‘, ’ 1 * ‘ 1 ’ a ’ * * ’ * ’ 1’. ‘. . f 

50 100 400 3150 63 0 12600 

I’ * 1’. “‘I. ‘1. * “*I ** I-” 50 100 200 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b)lZO' &140° 

Figure 7 1. -(Concluded) 

204 
96- 

94 - 

90. 

% 

I 

5 86. 

82. 

78 - 

OAsPL - NPR 2.2 

BOARDMAN STATIC DATA (30.5m) 

649m S/L (2128 ft) 

'PRI - 578 mls (1895 ft/s) 

-BASELINE 

-- 0--INVERTER/ZO[XER 

-----A----INV/HIXER/SHIE~ 

I , 

20 40 60 80 100 120 140 180 

102- 

98. 

86. 

ANGLE RELATIVE TO 1NL.m AXIS - deg 

Figure 72.-Comparison of Static OASPL and PNL Directivity, Baseline versus lnverter/ 

Mixer with and without Shield 

20s 
90 

1 

NPR - 2.1 

60' 

6 

g 

o 60 

d 

d 

& 4 40 

12210 SIDELINE (400 ft) 

. 

SYMBOL 1 TUNNEL 1 VpRI 1 VI 1 VR 1 UNITS i 

I I I I I I 

_--- 

1 OFF 1 573 I 23 I 5501 m/s I 

I 1 1870 1 75 I18031 ft/s I 

I ON 1 560 1 94 I 4661 m/s I 

I 1 1838 I 310 115281 ft/s 1 

I..’ * .I.- 1. .I .*I a.1 11 I..1 

-50 loo 200 400 800 1600 3150 6300 12600 

4o Lo..“.‘,.““.“‘.“.‘.” 50 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a)60° & SO0 

Figure 73.-Comparison of Tunnel-Off and -On Spectra, lnverter/Mixer Configuration 

206 
NPR - 2.1 

loo0 

ti 

: 50 L,..'..l..',.'..'..'..'..l 50 100 200 400 800 1600 3150 6300 12600 

60 

50 

120° 

,c 

1 . . 8.. 1% * 1 * ‘1 * * 1’. “-1. 400 3150 6300 * I 50 100 200 800 1600 12600 

ONE-THIRD OCTAVE BAND CENTER FREOUENCY - Hz 

(b) 100’ 81 120° 

Figure 73. -(Con timed) 

207 

- - 
NPR - 2.1 

140" 

2 \‘\ 

8 70 li2m SIDELINE (400 ft) \ 

0 

d SYMBOL 1 TUNNEL I VpRI 1 k= 1 VR 1 UNITS t 

Lj 

I I I I 

mm-- 

1 OFF 1 573 1 23 I 5501 4s I 

5 60 I 1878 1 75 118031 ft/s 1 

1 ON 1 560 I 94 1 4661 m/s 1 

I I 1 1838 1 310 115281 ft/S 1 

ti 

2 l..I..'..'..'.,""rI"' 

i 5oc50 100 200 400 800 1600 3150 6300 12ioo 

60 

t 

5o 1 5il ..1..1..1..‘~.‘..‘,,‘,,’ 100 200 400 800 1600 3150 6300 12600 

ONE-THIRD OCTAVE BAND CMTER FREQUENCY - Hz 

(c)140°& 150° 

Figure 73. -(Concluded) 

208 
lm/ 

i 

,’ /’ I’ !: 

NPR - 2.1 

60° 

80. 

70. 

60. 122m SIDELINE (400 ft) 

SYMBOL 1 TUNNEL I VpRI I VW. I VR IUNITSI 

I I I I I I 

50. ----I OFF 1 577 1 23 I 554 1 m/s 1 

I 1 1892 1 74 I 1818 1 ft/s 1 

-I ON 1, 570 1 79 I 491 I m/s I 

1 1871 I 261 I 1610 I ft/s i 

4oL 50 

I . I I * . I I I I . I 1 . . I , , 1 I , I . . 

400 a00 1600 3150 6300 12&o 

9or 80' 

6Cso40-5b 100 I1 I 200 I .., 400 , , 800 1 .,, 1600 , *, 3150 .., 6300 . . l2boO 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(a) So0 & 80’ 

Figure 74.-Comparison of Tunnel-Off and -On Spectra, lnverter/Mixer/Shield 

Configuration 
60. 

soSYMBOL 

----- 

;I 

122m SIDELINE (400 ft) 

1 TUNNEL I VpRI 1 VI I VR IUNITS 

I I I I I 

1 OFF 1 577 1 23 I 554 1 m/s 

ON 

1 1871 1 261 1 1610 1 ft/S 

go- 120° 

y;; 

60 

4o ' 5b ' ' do' '2:O' '4AO' '8;O ' '1;OO' '31150' '6;OO' i2bOO 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

(b) 100’ & 120° 

Figure 74. -(Continued) 

210 
100 NPR - 2.1 

140° 

122m SIDELINE (400 ft) 

-e--w 1 OFF I 577 I 23 I 554 I m/s I 

1 ON I I1892 570I 7491 I 1818 491lm/sI I ft/s I 

1 1871 I 261 I 1610 I ft/s) 

il..l..r..r..l..l..l..l..I 

50 100 200 400 0 1600 3150 6300 12600 

70 - 

60 - 

so- IL. 1 1 , I I I I I . . I I I I I I 1 I 

50 200 400 800 1600 3150 

. 1 

6300 12600 

ONE-THIRD OCTAVE BAND CENTER FREQUENCY - Hz 

Figure 74. -(Concluded) 

211 
NPR - 2.1 

OASPL 

76 

t 

649m SIDELINE (2128 ft) 

SYMBOL 1 TUNNEL I V,,, I V, I V, t UNITS I 

72 

I rnr n 

I 

1 OFF I 573 I 23 I ‘5501 m/s I 

-- 0 -- 

. I 1878 I 75 i18031 f;/s 

d-; ON 1 1884 574 1 264 80 I 116201 4941 ft/s m/s 

- I ON I 5601 9414661 m/s 1.i i 1838 i 310 ii5281 fi/s i 

68L 1 I 

20 40 60 80 100 120 140 160 

96- 

92 - 

% 88 - 

E 

A 

a 84- 

80. 

76 Lb I I I 

20 40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS - deg 

2.1 

Figure 75:Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

Inverter/Mixer Configuration 

212 
NPR - 2.1 

.OASPL 

88* 

84 - 

t 80 - 

1 

d 

9 

o 76 - 649m SIDELINE (2128 ft) 

SYMBOL I TUNNEL I VpRI I V, I VR IUNITS 

I I I I I I I I 

-- 0 -- 

1 OFF 1 577 I 23 I 554 I m/s 1 

1 1892 1 I I 

ON I 584 1 :i 1 'i:i 1 

:,s'/ / 

1 1916 1 189 I.1727 I ft/sl 

,+ 1 ON I 570 I 79 1 491 1 m/s ( 

1 1871 I 261 1 1610 1 ft/sl 

68L2y) i0 

I I I 1 60 80 100 120 140 160 

94 - 

90 

2 86' 

H 

I 

;I * 

82' 

78 

74 * , 

I 1 I I 20 40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE‘TO INLET AXIS - deg 

2.1 

Figure 76.-Comparison of Tunnel-Off and -On OASPL and PNL Directivities, 

In ver ter/Mixer/Shield Configuration 

213 
OASPL 

16 

16 

649m SIDELINE (2128 ft) 

n FROM 150 kn DATA 

n FROM 185 kn DATA 

1 I 1 

20 40 60 80 100 I 

120 140 160 

PNL 

A PNL 

n = 10 Log VPRI/VR 

20 40 60 80 100 120 140 160 

FAR FIELD ANGLE RELATIVE RELATIVE TO INLET AXIS - deg 

(a) NPR = 2.1 

Figure 77. - Velocity Exponents for OASPL and PNL, lnverter/Mixer Configuration 

214 
OASPL 

16 

SIDELINE (2128 ft) 

FROM 10~3 kn DATA 

FROM 150 kn DATA 

I I I 20 I 40 60 80 100 I 120 , 140 160 

PNL 

G 

z" APNL 

& n - 10 Log v PRI"R 

2 8 

I I I 20 I 40 -6Ci I 80 100 120 , 140 

FAR FIELD ANGLE RELATIVE TO INLET AXIS-&g 160 

lb) NPR = 1.8 

Figure 77. -(Concluded) 

215 
OASPL 

!s 

I 12- 64% SIDELINE .(2128 ft) 

E 

A n FROM 150 kn DATA 

B 

El- 

! 

s 

,k2 4- 

, 20 60 100 

1 40 80 120 140 160 

16 PNL 

FAR FIRLD ANGLE RELATIVE TO INLET AXIS -deg 

(a) NPR = 2.1 

Figure 78.- Velocity Exponents for OASPL and PNL, lnverter/Mixer/Shield Configuration 

216 
16- 

E: l2 

I 

E 

f f3- 

E 

s 

3 4- 

g 

oOASPL 

649m SIDELINE (2128 ft) 

0 n FROM 100kn DATA 

A n FROM 150 kn DATA 

L- 1 !- I 1 1 I J 

20 40 60 80 100 120 140 160 

PNL 

A PNL *- 10 Loi3 VPRI VR 

I- I I I I I I 1 

20 40 60 SO 100 120 140 160 

FAR FIELD ANGLE RELATIVE TO INLET AXIS- deg 

(b) NPR = 1.8 

Figure 78. -(Concluded) 

217 
eF - 60° 

649m SIDELINE (2128 ft) 

---o- - BOARWAN 30.5m OASPL 

--@-- 6OAiUMAN 30.h PNL 

-----.--- 40 by BOTUNNEL OFF 

n 40 by 80100 kn 

A 40 by ~0150 kn 

4 40 by 8018s kn 

P 1.6 

I 200 300 1 400 I 500 6dO 

PRIMARY RELATIVE JET VELOCITY (VFRr - Ve )-' m/S 

%O 

- 75 

-70 

2 

f 

d 

% 

-65 

(a) 60’ 

Figure 79. -Tunnel-Off and -On OASPL and PNL versus Primary Velocity, lnverter/Mixer Configuration 
649m SIDELINE (2128 ft) 

--O--BOARDMAN 30.5m 

BOARnnAN 3O.h 

-----a----40 by 80TlJNNEL 

l 40 by 80100kn 

A 40 by 80150 kn 

4 40 by 80185 kn 

OASPL 

PNL 

OFF 

eF - loo0 

‘1.4 

% 1.3 

._.~.~ Ic.-- 

200 300 400 500 660 

PRIMARY RELATIVE JET VELOCITY (VpRI - VI )- m/s 

-90 

e!i 

-70 

-65 

-60 

(b) 100’ 

Figure 79. -(Continued) 

219 
649m StDBLINE (2128 ft) 

B-0-d BOARDMAN 30:5m OASPL 

BOARDMAN 30.5m PNL 

---- -O----40 by BOTUNNEL OFF 

n 40 by 80 100 kn 

A 40 by 80 150 kn 

4 40 by 80185 kn 

-90 

a5 

- 70 

-65 

L 

200 300 400 500 660 

PRIMARY RELATIVE JET. VEMCITY (VPRr - V N )- m/s 

(cl 140° 

figure 79. -(Con timed) 
64901 hLI.NE !Zl;S ft) I 

b 

.F -150° 

--Oh --BoArmAd 3(1.5m OA Pi 

---C+-BOAEIMAtj 30.5~~ Pd 

;-. .--+pg b &gfp&Nl& Mfd ! . 

40 by 80 100 kn 

:I 40 by 80150k” 

+I 

40 by 80185 kn 

i 

I 

..- ‘I ..-. 

/ 

I 

i. .i.... 

i : 

I.... 

I /. 

i .: . . . . j ..-.. -.., j 

:I1 I 

1 / 

60 

I I 1 

200 300 400 500 

PRIMARY RELATIVE JET vm+m (onI - v m )- m/s 

6bb ; : 

j 

(d) 150' 

Figure 79. -(Concluded) 
95 

I 

90 

t 649~11 SIDELINE (2128 ft) 

I --Cl-- BOARDMAN 30.5m OASPL 

-O- BOARDMAN 30.5m PNL 

--•-- 40 by 80TUNNEL OFF 

8 40 by 80100 kn 

85 A 40 by 80150 kn 

2 

% = 60' 

d -A-C, (’ - I* / / / / 

-L--84 / / 

E 

a-7 

E 

80 - 

75 - 

70 - 

I I 1 

200 300 400 500 600 

PRIMARY RELATIVE JET VELOCITY (VpRr - V..)- m/s 

2.2 

-80 

-75 

-70 

% 

- 65 

- 60 

-55 

(a) 60’ 

Figure 80. -Tunnel-Off and -On OASPL and PAJL versus Primary Velocity, lnverter/Mixer/Shield Configuration 
100 lr 

95- 649m SIDELINE (2128 ft) 

--O-- BOARtHAN 30.5m OASPL 

-Cl- BOARDMAN 30.5m PNL 

--•-- 40 by SOTUNNEL OFF 

8 40 by 80100kn 

A 40 by 8u 150k.n 

90 - 

2 k 

E 85- 

a0 - 

75- 

OF = loo0 d 

A---o+ - 

/ / 

1’ 

-4g &--=-, / / / NPR 2.2 

d’ /’ 

1’ / 

/I 

,&.8 

/ 

p.4 

, 

200 300 400 500 640 

PRIMARY RELATIVE JET VELOCITY (VpRr - V, )- m/S 

(b)lOO' 

Figure 80. -(Continued) 

-85 

- 80 

-75 

: 

;;I 

z 

- 70 

-65 

-60 
102 - 

97, - 

AIRCRAFT DISTANCE: 649m (2128 Et) 

VELOCITY: 91.5 m/s (300 ft/S) 

BOARDMAN 30.5 m DATA 

= .EPNL WITHOUT F'LICfi EFFECT 

PLOTTED VERSUS VPRt 

---O---EPNL WITH40 by SOPLIGHT EFFECTS 

PLOTTED VERSUS (VpR, - V-a) 

92 - 

a7 - 

a2 - 

7714. 

PRIMARY vmJxITf - VPRI OR (VPRI - V@)4l/S 

Figure 8 1. -Static and Estimated Flight EPNL Characteristics, lnverter/Mixer Configuration 

226 
107 - 

102 - 

97 - 

% 

b 

I g2- 

E w 

87 - 

82 . 

77 - 

AIRCRAFT DISTANCE: 64% (2128 ft) 

VELOCITY: 91.5 l/S (300 ft/s) 

BOARDUAN 30.h DATA 

ti EPNL WITHOUT FLIGHT EFFECT 

PLOTTED VERSUS VpRI 

----O---- EPNL WITH40 by SOfiIGHT EIFRCTS 

PLOTTED VERSUS (VpRI - V,) 

2.2 

1 

200 300 400 500 

PRIllARY VELOCITY - VpRI OR (VpRI - VW l-a/a 

630 

Figure 82. -Static and Estimated Flight EPNL Characteristics, lnverter/Mixer/Shield Configuration 

227 
987 987 STATIC 

SIDELINE - 64% (2128 ft) 

V - m/s 

94-4- PRI PRI - 578 m/s (1895. ft/s) 

------ INVERTER 

-----------INVERTER/PLIJG 

90- go- ---INvERTER/NIxEB 

----INV./MIXER/SRIELD 

s 

?ll 

5 

2 86- 

82- 

?8- 

92- FLIGHT 

88. VI- 91.5 m/s (300 ft/St 

84- 

Q I 

2 

Y 

o SO76- 

72L 20 I I I I t I I 1 

40 60 80 100 120 140 160 

FAR FIELD ANGLE REUTIVE TO INLET AXIS - dw 

Figure 83.-Comparison of Static and Flight OASPL Directivity for Baseline and Inverted 

Flow Suppressors 

228 
102- STATIC 

SIDELINE - 649m (2128 ft) 

V PRI - 578 m/s (1895 ftfs) 

98- 

BASELINE 

---LWERTEP 

----------INVERTERfPLUC 

m 94- ---INVERTERf MIXER 

I 

----INV./MIXERfSHIELD 

; 

h QO86 - 

\ 

82- 2’0 I L- .- 1 J 1 I \ , 

40 60 00 100 120 140 160 

96 FLIGHT 

60 - 

\ A 

160 76L2- -~ lo L I , I . 

. 

60 80 100 120 140 

FAR FIELD ANGLE REMTIVE TO INLFT AXIS - deg 

Figure 84.-Comparison of Static and Flight PNL Directivity for Baseline and Inverted 

Flow Suppressors 

229 
lO7- 

102,- 

971- 

a2 - 

77 - 

AIRCRAFT DISTANCE: 649m (2128 ft) 

VELOCITY: 91da (300 ft/J) 

BOARDHAN 30.5m DATA WITHOUT 

40 by SOFLIGHT EFFECTS 

- BASELINE 

--0--1NVERTER 

---- A ----INVERTER/PLUC 

-- 6 -- INVERTER/MIXER 

----D---WVERTER/HIXER/SHIttD 

NPR 2.2 

/ 

, 

200 300 400 500 680 

PRIMARY VELOCITY - V PRI -m/S 

Figure 85.-Comparison of Baseline and Inverted Flow Suppressor EPNL, Static Levels 

230 
107,, 

102'. 

97 . 

m -0 

E 929 

I 

s 

3 

87 - 

82 - 

77L 

AIRCRAFT DISTANCE: 649m (2128 ft) 

VELOC1l-f : 91.5m1s (300 ft/s) 

BOARDMAN 30.5m DATA WITH 

40 by 8r)FLICRT EFFECTS 

.- BASELINE 

-O- INVERTER 

---A--- INVERTERjPLDC 

.- -. 0 INVERTER/MIXER 

..-fJ-.. INVERTER/MIXER/SH1EL 

I 200 1 I 300 400 500 

PRIMARY VELOCITY - VpRI-m/s 

6.80 

Figure 86.-Comparison of Baseline and Inverted Flow Supressor EPNL, Flight Levels 

231 

- - 
l.O0.98 - 

0.96 - 

*t 0.94 - 

; 

3 

:: 0.92 - 

s 

s 

c 2 0.90 - 

m 

nz 

B o.aa0.86 - 

0.84 - 

JTBD-17R ENGINE 

UITA BELL mWli INLET 

0 BASELINE 

AA INVERTER 

0 INVERTER/PLUG 

Cl INVERTERhIXER 

cv - 

MEASURED THRUST 

IDEAL THRUST OF K%WRED MSS FLOW 

o.a2L 

I 

1.0 1.2 1.4 1.6 1.8 2.0 2.2 

ENGINE PRESSURE RATIO - PTM7/Pamb 

(a) With Bell Mouth Inlet 

Figure 87.-Comparison of Engine Thrust Coefficients 

232 
1.0 

0.98 

0.96 

c 

0 0.94 I 

=: 

2 

$ 0.9c 

2 

s 

zi 

o.ae 

0.86 

0.84 

0.8i 

JTSD-17R ENGINE 

WITH Z-RING INLET 

0 INVERTERfMIXER 

n INVERTERfMIXER 

WITH SHIELD 

‘ 

1.2 1.4 1.6 1.8 2.0 2.2 

ENGINE PRESSURE RATIO - PTM7/Pamb 

(b) With Z-Ring Inlet 

Figure 87. -(Concluded) 

233 
TfST ZSSZTF - Jr00 :NVE*lLD FLGY TEST - PHASE 1 - STATIC TESl 

1rtvrarca EXIT FLOU SuavEI I PaE55UaE PLOT I 

CONFIG - Z-RING INLET, CLOU INVERtEa. PC NOZZLE 

1 206.8 N/M2 

2 203.4 

3 199.9 

4 196.5 

5 193.1 

6 189.6 

A 172.4 

0 168.9 

c 165.5 

D 162.0 

E 158.6 

TEST NO. 2552 TEST DATE 20177 30577 

RUN NO. 19 CONO. N+ 1 109.7 

TAPI0 DEGC 0 Plf N/m 211.7 194.0 

117 DEGC 513 TlF7 DEGC 76 PTf/PAMB 2.102 

PTF7/PhnB 1.926 VPRI m/s 551 VFAN mlr 346 

Figure 88. -In verter Exit Flow Survey (Pressure Plot) 

234 
TEST 25S2~? - JlgD :NvERTCO FL~U lE51 - pm*SE I - 5TATIt TE5’ 

INVCPTEI CxIT FLDU SuavfT I rcmPEa*ruaE ~~07 1 

tONFIt - Z-RING INLET. rLOU INVfr)TEn. Qc NOZZLE 

1 505 oc 6 810 

2 449 

3 393 

4 365 

5 338 

A 171 

0 143 

C 115 

Q 88 

E 60 

TEST NO. 2552 

RUN NO. 19 

TAHB OEGC 0 

117 DEGC 513 

PlF7/PAflB 1.926 

TEST DATE 20177 CALC. DATE 30977 

LUND. NO. 1 

N/l? 

PAflB N/m* 100.7 

Pf7 211.7 PfF7 N/m2 194.0 

lTF7 OEGC 76 Pl7/PAHB 2.102 

VPRI m/s 551 VFAN m/s 346 

Figure 89.4nverter Exit Flow Survey (Temperature Plot) 

235 
ttlt ZSIQTP .- JTaa INvCRlCD FLOU TC31 - PIUSE 1 - STATIC Tf5T 

INVCRTER CxIT FLOu CuWCT t v~LBCITT PLOT 3 

EDWIG - Z-RING INLfT. FLOLI INvEQTE~. QC NOZZLE 

I 503 m/s 

2 488. 

3 457 

4 427 

5 412 

6 396 

A 320 

0 305 

t 290 

D 274 

tE5T NG. 

RUN Nfl. 

TAME DEGC 

117 OEGC 

PfF I/PAM 

2ss2 TEST DATE 20177 30977 

19 CUNO. NO. a 

CALC. DA!E 

PAIIB N/m 100.7 

0 PT7 N/m* 211.7 PtF7 N/m* 194.0 

513 lTF7 DEGC 76 Ptt/PAllB 2.~02 

1.926 VPRI m/s 551 VIAN m/s 346 

Figure 90.-lnverter Exit Flow Survey (Velocity Plot) 

236 
104r OASPL 

loo92 - 

TAKEOFF POWER 

457~1 SIDELINE (1500 ft) 

-BASELINE 

-----INVERTER 

--INTERNAL KtXER 

aa 

1 

a4 1 L I 60 80 100 120 140 160 

108- 

104 - 

2100 - 

3 

d 

96 - 

92 - 

I asL 60 

I I 80 100 120 140 160 

ANGLE RELATIVE To INLET AXIS - deg 

Figure 91.-Comparison of Model Static OASPL and PNL Directivity, Baseline, lnverter, 

and Internal Mixer 

237 
llO106 - 

a 

3 9’02 - 

: 

2 h 98 - 

94 - 

(1500 

-A- UQDEL DATA 

-- O--FULL SCALE DATA 

I I 

INVERTED FLOW UNINVERTED FLOW 

-I- 90 t 

1.3 1.2 1.1 1.0 1.2 1.3 

VELOCITY RATIO - 

VpR& 

ft) 

Figure 92.~Model and Full Scale Peak PNL versus Velocity Ratio 

238 
4. Title and Subtitle 

Flight Effects on Noise Generated by the JTSD Engine with 

Inverted Primary/Fan Flow as Measured in the NASA-Ames 40- 

by SO-Foot Wind Tunnel 

-- .-~ ~~--_- - _ 1 

7. Author(s) 

5. Report Da& 

June 1978 

6. Performing Organization Code 

~-- -.__ 

8. Performing Organization Report No. 

Frank G. Strout 

10. Work Unit No. 

9. Performing Organization Name and Address 

Boeing Connnercial Airplane Company 

P. 0. Box 3707 11. Contract or Grant No. 

Seattle, Washington 98124 NAS Z-9302 

13. Type of Report and Period Covered 

12. Sponsoring Agency Name and Address 

National Aeronautics and Space Administration 

Ames Research Center 

Moffett Field, California 

I5 Supplementary Notes 

Contractor Report 

14. Sponsoring Agency Code 

3. Recipient’s Catalog No. 

16. Abstract 

A JT8D-17R engine with inverted primary and fan flows was tested under static conditions and in 

the NASA Ames 40- by do-Foot Wind Tunnel to determine static and flight noise characteristics. 

The major purpose of the program was to evaluate flight effects on noise generated by the inverted 

flow profile of a large scale engine. The jet noise suppressor concept is of particular interest 

to Advanced Supersonic large scale engine. The jet noise suppressor concept is of particular 

interest to Advanced Supersonic Transport engine cycle studies where high jet velocities create 

a serious noise problem during takeoff operation. Test and analysis techniques developed by a 

previous model and JT8D enginer test program (NASA CR-2841 and CR-2576) were used to determine 

the in-flight noise. The engine with inverted flow was tested with a conical nozzle and with 

Boeing supplied nozzle hardware including a plug nozzle, 20 lobe nozzle, and an acoustic shield. 

Wind tunnel results show that forward velocity causes significant reduction in peak PNL suppressio 

relative to the uninverted flow. The loss of EPNL suppression is relatively modest. The in-fligh 

peak PNL suppression of the inverter with conical nozzle was 2.5 PNdB relative to a static value 

of 5.5 PNdB. The corresponding EPNL suppression was 4.0 EPNdB for flight and 5.0 EPNdB for 

static operation. The highest in-flight EPNL suppression was 7.5 EPNdB obtained by the inverter 

with 20 lobe nozzle and acoustic shield. When compared with the JT8D engine with internal mixer, 

the inverted flow configuration provides more EPNL suppression under both static and flight 

conditions. 

7. Key Words (Suggested by Author(s) I 

Jet Noise Suppressor Nozzles 

Source Locations Flight Effects 

Large Scale Wind Tunnel 

Inverted Flow 

.- 

9. Security Qassif. (of this report) 20. Security Classif. (I 

18. Distribution Statement 

Unclassified, Unlimited 

Star Category - 07 

this page) 21. No. of Pages 22. Price* 

Unclassified I Unclassified I -...2?c 1 $9.50 

*For sale by the National Technical Information Service, Springfield, Virginia 22161 

NASA-Langley, 1978