NASA Technical Memorandum 87698

Wind-Tunnel Acoustic Results

of Two Rotor Models With

Several Tip Designs

(NASA-TM-87698) WIND-TUNNEL ACOUSTIC N86-28701

RESULTS OF TWO B010R MODELS WITH SEVERAL TIP

DESIGNS (NASA ) 1.91 p HC A09/MF A01 .CSCL 20F

Uaclas

G3/71 43358

R. M. Martin and Andrew B. Connor

JULY 1986

NASA
NASA Technical Memorandum 87698

Wind-Tunnel Acoustic Results

of Two Rotor Models With

Several Tip Designs

R. M. Martin and Andrew B. Connor

Langley Research Center

Hampton, Virginia

NASA

National Aeronautics

and Space Administration

Scientific and Technical

Information Branch

1986
CONTENTS

SUMMARY 1

INTRODUCTION 1

SYMBOLS 2

DESCRIPTION OF EXPERIMENT 3

Wind-Tunnel Facility 3

Rotor Model System 4

Test Procedure 4

Acoustic Data Acquisition 5

Acoustic Data Reduction 6

DATA QUALITY 7

Background Noise 7

Reflections 8

Geometric and Acoustic Near-Field 9

Refraction 9

Repeatability 9

Summary of Data Quali ty 10

DISCUSSION 10

Near-Field Location 10

Under Flight Path 12

Above Rotor Disk Plane 12

In Rotor Plane 13

Advancing Side 13

Retreating Side 13

Comparison of Rotor Systems 13

Operating Conditions for Minimum Noise Levels 14

CONCLUDING REMARKS 14

REFERENCES 16

TABLES 18

FIGURES 23

APPENDIX A - COMPARISON OF OVERALL ACOUSTIC LEVELS FROM

TWO ANALYSIS METHODS 68

APPENDIX B - REPRESENTATIVE TIME HISTORIES AND NARROWBAND

SPECTRA FOR SELECTED TEST POINTS IN APPENDIX A 159

PRECEDING PAGE BLANK NOT FILLED

iii
SUMMARY

A three-phase research program has been undertaken to study the acoustic signals

due to the aerodynamic interaction of rotorcraft main rotors and tail rotors. During

the first phase, two different rotor models (a high-twist system and a low-twist system) with several interchangeable tips were tested in the Langley 4- by 7-Meter

Tunnel on the U.S. Army rotor model system. An extensive acoustic data base was acquired, with special emphasis on blade-vortex interaction (BVI) noise. The details

of the experimental procedure, acoustic data acquisition, and reduction are documented. The relative importance and trends of the noise characteristics for the nine

rotor systems are also discussed.

It is shown that the overall sound pressure levels (0 to 12 700 Hz) of the hightwist rotor systems are relatively insensitive to flight speed but generally increase

with rotor tip-path-plane angle. The overall sound pressure levels of the high-twist

rotors are dominated by acoustic energy in the low-frequency harmonics, rather than

by energy at a higher frequency. The overall sound levels of the low-twist rotor

systems show more dependence on flight speed than the high-twist rotors, in addition

to being quite sensitive to tip-path-plane angle.

A midfrequency, integrated band-limited sound pressure level, limited by 500 to

3000 Hz, is shown to be a useful metric to quantify the occurrence of BVI noise. The

overall sound pressure levels of the low-twist rotors are also strongly influenced by

the midfrequency band-limited sound levels (500 to 3000 Hz), indicating that the

blade-vortex impulsive noise is a more dominant noise source for this rotor design

than for the high-twist rotors. The midfrequency acoustic levels for both rotor

systems show a very strong dependence on rotor tip-path-plane angle. The tip-pathplane angle at which the maximum midfrequency sound level occurs consistently decreases with increasing flight speed. The maximum midfrequency sound level measured

at a given location is constant regardless of the flight speed.

INTRODUCTION

The Langley Research Center, the U.S. Army Aerostructures Directorate, and

Sikorsky Aircraft have jointly undertaken a rotor acoustics research program. The

primary objective of the effort is to study the acoustic signals due to the aerodynamic interaction of helicopter main rotors and tail rotors. Additional objectives

are (1) to characterize the impulsive noise due to blade-vortex interaction (BVI)

created by various blade tip geometries as a function of rotor operating parameters,

(2) to characterize the noise of tail rotors and tail rotor installation effects,

(3) to acquire an acoustic data base for use in the development and validation of a

BVI noise prediction method, and (4) to make comparisons with other scaled acoustic

data.

The program is being conducted in three phases. The first of these, the scope

of this paper, treats the main rotor alone. This test was conducted in 1983 in the

Langley 4- by 7-Meter Tunnel with two rotor systems. The two systems were similar in

planform, solidity, and blade number. They differed in airfoil section details,

twist distribution, chord, and geometry of their several interchangeable blade tips.

The second phase of the program was conducted in 1984 by Sikorsky at the United
Technologies Research Center (UTRC) anechoic wind tunnel with two tail rotor models

and various pylon-stabilator configurations. The third phase was conducted in 1985

in the Langley 4- by 7-Meter Tunnel where selected configurations from phases I and

II were tested in a full experiment of the noise interaction between the main rotor

and tail rotor.

\

One of the least understood and most troublesome of the many helicopter noise

mechanisms is the blade-vortex interaction. This phenomenon typically occurs during

low-power descending flight or maneuvers or during conditions of low rotor inflow

when the rotor wake is blown back into the rotor disk. The concentrated tip vortices

shed from the blade tips are embedded in the rotor wake. Interaction of a blade with

the shed tip vortex of a previous blade passage gives rise to the distinctive BVI impulsive noise. The local aerodynamic flow field that generates the impulsive signal

is strongly dependent on the orientation and proximity of the vortex to the blade.

The impulsive acoustic signal is generally in the frequency range most sensitive to

human subjective response (500 to 5000 Hz) and thus has importance to both civil community acceptance and military detectability.

Some acoustic results of the phase I experiment have been previously published.

The data were first applied in an acoustic-ray tracing technique (ref. 1) to determine the region on the rotor where the blade-vortex interactions occurred. The

experimental results were compared with analytic predictions of blade-vortex encounters using a generalized rotor-wake prediction code (ref. 2). The acoustic data

have also been compared with 1/20- and full-scale acoustic data in work reported by

Shenoy (ref. 3). This paper is intended to document fully the details of the phase I

experiment and to present a summary and general analysis of the results.

SYMBOLS

Values are given in SI Units but, where considered useful, they are also given

in U.S. Customary Units. Measurements and calculations were made in U.S. Customary

Units.

o

A acoustic pressure amplitude, dynes/cm

AO peak acoustic pressure amplitude, dynes/cm2

C chord of rotor blade, m

c speed of sound, m/sec

f frequency, Hz

K acoustic wave number, 2itf/c, m

£ distance from center of rotor tip path plane to microphone, measured in

rotor tip path plane, (x2 + y2)

1

/

2

, m

R rotor radius, 1.42 m (4.67 ft)

r radial distance from center of rotor tip path plane to microphone,

(x2 + y2 + z2)

1

/2f m
At elapsed time from echo, sec

V tunnel free-stream velocity, m/sec (knots)

x microphone coordinate relative to center of rotor tip path plane, positive

upstream, m

y microphone coordinate relative to center of rotor tip path plane, positive

to left looking upstream, m

z microphone coordinate relative to center of rotor tip path plane,

positive up, m

a 'rotor tip-path-plane angle, also called "rotor angle of attack" (see

subsection entitled "Rotor Control"), positive when vehicle nose is up,

deg

9 polar angle, angle down from rotor tip path plane, positive down,

tan~1(z/£), deg

i|> azimuth angle, angle in plane of rotor, positive counterclockwise, zero

over aircraft tail, tan~1(y/x), deg

Abbreviations:

BLSPL band-limited sound pressure level (500 to 3000 Hz), dB

(re 0.0002 dynes/cm2)

BVI blade-vortex interaction

ITS locations inside tunnel test section

Mic. microphone location

OASPL overall sound pressure level (0 to 12 700 Hz), dB (re 0.0002 dynes/cm2)

OTS locations outside tunnel test section

DESCRIPTION OF EXPERIMENT

Wind-Tunnel Facility

The Langley 4- by 7-Meter Tunnel is a closed-circuit atmospheric wind tunnel

that can be operated either in the open-jet or closed-jet mode. The open-jet mode is

accomplished by removing test section walls, raising a movable ceiling, and introducing a bell-mouth collector. The dimensions of the rectangular jet facility when

operated as an open-jet test chamber are 4.42 m (14.50 ft) high and-6.63 m (21.75 ft)

wide. The ceiling in the open-throat configuration is approximately 7.50 m

(24.60 ft) above the test chamber floor. The floor of the test section remains in

place so that three sides of the jet are open. The rotor model and test rig in the

open-jet test chamber are shown in figure 1.
The acoustic characteristics of this facility as originally constructed have

been documented (ref. 4). Because this facility was not originally designed for

acoustic testing, acoustic treatment was applied during the experiment reported

herein to reduce acoustic reflections from the walls, floor, and ceiling of the test

chamber. The test section floor was lined with 12.7-cm (5.0-in.) fiberglass panels

covered with perforated sheet metal. The floor, ceiling, and wall areas adjacent to

the test section were covered with 15.2-cm (6.0-in.) open-cell polyurethane foam.

The locations of this acoustic treatment, identified by the crosshatched areas, are

shown in figure 2. The effects of this acoustic treatment and the accuracy of the

resulting acoustic data are discussed in the section entitled "Data Quality."

In addition to acoustic treatment, small triangular vanes were installed around

the inside perimeter of the jet exit. The purpose of these vanes was to reduce a

low-frequency flow pulsation (refs. 5 and 6) that occurred at low speeds in the openjet mode. Initially, these vanes increased the tunnel background noise levels;

however, some innovative treatment was applied and the noise created was restored to

that of the unmodified tunnel (refs. 7 and 8).

Rotor Model System

Two four-bladed rotor models were tested using the general rotor model system

(GRMS) described in reference 9. The GRMS is employed by the U.S. Army Aerostructures Directorate for rotor systems research in the Langley 4- by 7-Meter Tunnel.

Details of the two rotor models are presented in figures 3 and 4, which show their

planform, twist, and tip configurations. Other pertinent data for these models are

listed in table I. These particular rotor blades and tips were chosen for two reasons: they represent contemporary technology in rotor and tip design and there is a

considerable amount of full- and model-scale data available for the same designs.

The high-twist model was a 17-percent-scale model, and the low-twist model was a

21-percent-scale model of the full-scale rotors. The fuselage model employed was a

generic fuselage shape of approximately the same scale as that of the high-twist and

low-twist rotor systems.

High-twist rotor and tips.- The rotor blade for the high-twist model is shown in

figure 3 and the blade tips are shown in figure 4. The four tips are standard, swept

tapered with an SC1095 airfoil section, swept tapered with an SSC-A07 airfoil

section, and parabolic with an SSC-A07 airfoil section.

Low-twist rotor and tips.- The low-twist rotor blade and tips are also shown in

figures 3 and 4. The five tips are standard, anhedral, swept, tapered, and square.

This rotor model is described in detail in reference 10.

Test Procedure

Test conditions.- The research objective was to map the noise generation as a

function of forward speed and tip-path-plane angle at fixed thrust coefficient for

each rotor configuration, with emphasis on the measurement of BVI impulsive noise.

The rotors were tested over a speed range from 50 to 80 knots at tip-path-plane

angles ranging from -6° to 10°. The rotor test matrices reported here are shown in

figure 5. Other parametric variations were measured, such as tip speed ratio, thrust

coefficient, and tip Mach number, but they are not reported here. Forward speed and

tip-path-plane angle were the principal operating parameters. The range of tip-pathplane angle was intended to bracket the region of minimum BVI noise, the onset of BVI
noise, and the maximum BVT noise at each flight speed. The tunnel background noise

levels at high speeds limited the tunnel speed to less than 90 knots. At low speeds,

large open-jet aerodynamic boundary corrections, in addition to a low-frequency aerodynamic pulsation in the open-jet tunnel, limited the tunnel speed to greater than

40 knots.

Rotor control.- Conventional helicopter terminology will be employed throughout

this paper in the discussions about and descriptions of these test rotors. Readers

not familiar with these terms and conventions are referred to a classical text such

as reference 11.

The rotor tip-path-plane angle a was set by setting the rotor shaft angle. To

ensure that rotor shaft angle, or rotor angle of attack, and tip-path-plane angle

were essentially equal, flapping angles were set to 0 with cyclic pitch control. The

procedure was to trim the rotor to zero flapping for a given tunnel speed and to step

the rotor angle of attack in 2° increments at each speed. The nominal rotor angles

of attack were corrected for the actual tunnel flow conditions; thus the data will

usually be given in some value approximating an integer step of 2°. The nominal

value of a, rather than the corrected value, will customarily be presented here for

simplicity. To change rotor angle of attack, the rotor hub was pivoted about a

reference point approximately 73.7 cm (29 in.) below the rotor hub. Thus, when the

rotor angle of attack was changed, the physical location of the rotor hub in the test

section changed also. Collective pitch was adjusted after each angle-of-attack

change to maintain a constant thrust coefficient.

Rotor performance data.- Rotor performance data (ref. 12) were acquired using a

computer-controlled data acquisition system. The performance data were acquired

while the acoustic signals were recorded on tape in order to relate the character of

the noise to rotor operating parameters. Cyclic and collective pitch angles were

measured at the swashplate, blade flapping and lag angles were measured at their

hinge pins, and the entire system was mounted upon a six-component strain-gauge balance to measure rotor forces and moments. The rotor performance parameters were continuously computed and updated from these measurements during the test. Upon achieving a steady-state operating condition, all data were acquired and stored for later

processing. The later processing included cross-plotting of rotor thrust coefficient, flapping angles, and rotor moments to ensure that the acoustic data were

acquired at the correct operating conditions. The mean flow angle and mean freestream velocity of the tunnel were corrected for open-jet boundary effects using the

theory of reference 13.

Acoustic Data Acquisition

Nineteen 0.635-cm-diameter (0.25-in.) free-field condenser microphones were

installed in and around the open-throat test section as shown in figure 2. These

particular locations were chosen initially with the intention of acquiring acoustic

data at several specific angles relative to the rotor disk (9) for a range of azimuth

angle in the disk plane (if;). The exact locations in terms of Cartesian coordinates

(x, y, z) and in terms of the radial distance, angle below the disk plane, and azimuth angle (r, 9, iji) are presented in table II; the orientation of these two coordinate systems is also shown. Inspection of table II shows that several microphones

were located at angles of 9 near 25°, near 0° (in the disk plane), and near -25°.

The azimuth angle t|> varied in multiples of 45° from 45° to 270°.
Microphone 1 was mounted to the fuselage, very close to the rotor disk, in a

location known to be sensitive to BVI noise. The geometry between the rotor hub and

this microphone remained constant with rotor attitude change. Since all the other

microphones were fixed to the test chamber floor, their relative locations changed

with changes in rotor shaft angle. This condition means that for these locations, a

true assessment of directivity cannot be made. The changes in polar angle 9, radial

distance r, and azimuth angle ip with changes in rotor angle a are presented in

tables III, IV, and V, respectively.

The acoustic data were recorded on two 14-channel frequency-modulated magnetic

tape recorders. A once-per-revolution impulse signal was recorded on magnetic tape

simultaneously with the acoustic signals to record blade azimuth angle, in addition

to IRIG-A time code. The recording method was Wideband I and the tape speed was

76.2 cm/sec (30 in/sec). Daily calibrations were performed using a standard pistonphone calibrator at 250 Hz, 124 dB. The analog signals were not-high-pass filtered

(as is often done to remove low-frequency wind noise) because of the phase distortion

of the available filters. (Since the impulsive time history was of primary interest

to this study, nonlinear phase distortion could seriously alter the waveforms, particularly at low frequencies near the filter cutoff frequency.)

Each complete microphone system (including the microphone, preamplifier, and

adapter) was calibrated using the electrostatic actuator method prior to the experiment for its pressure response. This response was found to be flat to approximately

7 kHz, at which the correction was approximately -0.5 dB and became as much as

-1.4 dB at 10 kHz. Typical rotor acoustic spectra acquired during this experiment

had the highest levels at the first few blade passage harmonics (100, 200, and

300 Hz). The rotor acoustic levels at 7 kHz were typically 30 dB lower than these

low-frequency levels. In this case the pressure response corrections would not have

a measurable effect on the results, and therefore the corrections were not applied.

To verify the frequency response characteristics of each acoustic data acquisition system, an in-line white noise signal was inserted simultaneously into each data

channel. The relative time error between each data channel was calculated from the

phase of the cross power spectral density function of the white noise for each unique

pair of channels. The relative time error between channels was found to be small

enough (approximately 20 percent of the time between digitized samples at a sample

rate of about 26 000 samples per second) that it could be considered negligible.

Acoustic Data Reduction

The analog acoustic signals were digitized using a conditional sampling technique based on the rotor once-per-revolution signal. A synchronizer sampled the

acoustic signals at 1024 equally spaced intervals in each rotor revolution such that

the 1024 points defining each rotor revolution are at the same relative azimuth angle. The synchronizer constantly updated the sample rate to adjust for small changes

in rotor rotational speed. The acoustic time histories of 50 rotor revolutions were

sampled in this manner and then were ensemble averaged to obtain an average acoustic

waveform and standard deviation for each test condition. The effect of this averaging technique is to remove random fluctuations such as background noise and to enhance the periodic content of the signal. , The averaged time history, standard

deviation band, and five revolutions of instantaneous time history data were stored

on a computer disk.
To obtain spectra, 200 rotor revolutions were conditionally sampled, and the

data of four sequential rotor revolutions were transformed to the frequency domain

using a 4096-point fast Fourier transform algorithm. This approach yielded 50 spectra with a bandwidth of exactly 1/16th of the blade passage frequency. The results

of each of these 50 power spectra were then averaged to get an average power spectrum

for each test condition, which was stored on a computer disk. Considering each power

spectrum as a Chi-squared random variable, the statistical accuracy of the spectral

results is ±0.8 dB for an 80-percent confidence interval.

It should be noted that a time domain weighting or spectral window was not

applied to these data. The harmonic analysis approach employed minimizes leakage of

the acoustic energy at the blade passage frequency and its harmonics, and thus a

Banning or other window is not required. In addition, since the digitization rate

was tied to the rotor shaft speed, which varied slightly during each recording

sequence (±2 rpm at 1480 rpm), the spectral calculations are actually estimates of

the acoustic energy at multiples of the shaft frequency, rather than at particular

frequencies. However, since the variation in rotor rotational speed was very small,

the variation in sample rate was also small, and thus the error in the nominal frequency is very small (typically 6.7 Hz ± 0.0002 Hz for the high-twist system data and

5.8 Hz ± 0.003 Hz for the low-twist system data).

To obtain integrated sound pressure levels, the squared acoustic pressures of

the power-averaged spectra were summed from 0 to 12 500 kHz for an overall sound

pressure level (OASPL) at each rotor test condition, and they were summed from 500 to

3000 Hz to acquire a band-limited sound pressure level (BLSPL). Since the overall

levels of rotors are often dominated by the low-frequency levels, this band-limited

sound level was calculated to emphasize changes in the midfrequency range. The range

of 500 to 3000 Hz was chosen because changes in model scale BVI noise levels were

observed to be the most significant in this region.

DATA QUALITY

The Langley 4- by 7-Meter Tunnel was not originally designed for acoustic

research, and thus there are fundamental limits to taking acoustic data in the facility. At the higher tunnel speeds (above 90 knots), the major limiting factor is tunnel background noise. At lower speeds (less than 40 knots), a low-frequency flow

pulsation has been a problem in the past (ref. 5). Work is currently underway

(refs. 6 and 14) to provide solutions to these aerodynamic and acoustic problems.

The following paragraphs describe some of these factors that may affect the quality

of the acoustic data acquired. A summary is presented at the end of this section.

Background Noise

Background noise data were acquired for all microphone locations with the model

installed, the rotor hub spinning (without rotor blades), and for tunnel speeds from

50 to 120 knots in 10-knot increments. For all the microphone locations, the predominant noise is the low-frequency tunnel background noise, which typically decreases

by 25 to 30 dB at 1000 Hz. The background noise above 5000 Hz is generally near the

noise floor of the recording system for a system with approximately 40 dB of dynamic

range. An example of the background noise spectra for a typical inflow location

inside the tunnel test section (ITS) at 50 to 90 knots is shown in figure 6.
Figure 7 shows the overall background noise levels for microphone locations 1,

2, 3, 4, 5, 9, 12, and 17 as a function of tunnel speed. The lowest noise levels

over the range of tunnel speed are at locations 1, 3, and 4. Higher levels are exhibited by locations 2 and 17; those in the middle are locations 5, 9, and 12.

Figure 8 shows the background noise levels for the microphones located outside

the tunnel test section (OTS) and split into two groups. The first group (microphone

locations 7, 8, 16, and 19) exhibits the lower overall levels (fig. 8(a)), the second

group (microphone locations 10, 11, 13, 14, 15, and 18) exhibits the higher levels

(fig. 8(b)). The first OTS group has lower overall levels than the ITS locations,

but most of the second OTS group have higher levels than the ITS. It was observed

during the test that this latter group of OTS microphones experienced a great amount

of wind-induced noise and that they were too close to the tunnel jet shear layer.

Calculations made prior to the test (based on a shear layer expansion angle of 15°)

indicated that these locations would be outside the jet shear layer and in a relatively quiet environment; however, this was not the case. It is probable that the

use of the jet exit vanes, which were used to reduce pulsations in the jet shear

layer, also increased its thickness significantly (refs. 5 to 7).

Several typical rotor test conditions were chosen and the rotor and background

data were plotted together. For the ITS microphones, the signal-to-noise ratio is

good except at the very lowest frequencies where the wind noise can be quite close to

the lowest rotor harmonics. An example of this comparison is shown in figure 9.

Since the background noise levels were relatively high at the higher tunnel

speeds, the integrated sound pressure levels and the averaged acoustic spectra were

corrected by subtracting the background noise on an acoustic power (mean-squared

pressure) basis. The time history data have not been corrected for background

noise. The effect of averaging time histories serves to remove some random energy.

Reflections

To measure reflections at each microphone, small explosive charges were ignited

in the test section to create an impulsive noise source at each of the following

tunnel speeds: 0, 50, 80, and 120 knots. The acoustic signals were recorded on tape

and analyzed to measure the reflections at each microphone location. The impulse

signal had most of its energy in the spectral region from 0 to 3000 Hz; and because

of the very short period of the emitted impulse, the signal was very useful in

identifying reflections with very short path lengths (approximately 30 cm (1 ft)),

such as those arriving from some of the microphone support stands. An example of the

impulse data and reflections measured at zero tunnel speed is shown for microphones 1

and 3 in figures 10(a) and 10(b), respectively. The direct and echo signals are

marked in this figure. Table VI contains the estimated reflection delay times, relative amplitudes, and possible reflecting surfaces for all the microphones for the

0- and 80-knot cases. Most of the reflections have relative amplitudes in the range

from 0.1 to 0.3, or about 20.0 and 10.5 dB down from the incident wave. Since the

accuracy of the spectral averaging method is ±0.8 dB, a reflection with a relative

amplitude less than 0.4 (which adds 0.6 dB to the total rotor signal) has an effect

on the integrated acoustic results that is less than the uncertainty of the data

reduction approach.

A tone burst generator was also used in the test section to generate short

bursts of pure tones at frequencies of 500, 1000, 3000, and 5000 Hz. Inspection of

these data confirmed the results of the impulsive source data. Examples of the tone

8
burst data for microphone 1 at 1000 Hz and microphone 3 at 500 Hz are shown in figures 11(a) and 11(b), respectively. The direct and reflected signals are marked in

these figures. In general, the 500-Hz tones exhibited the highest reflection amplitudes. This result indicates that the low-frequency content (less than 1000 Hz) of

the rotor signal may be more contaminated by reflected signals than the higher frequency content (greater than 1000 Hz).

In an attempt to correct the measured rotor acoustic spectra for the reflection

contamination, the power cepstrum technique was investigated (ref. 15). The power

cepstrum is a Fourier transform technique that has been used to correct acoustic

reflections from contaminated jet noise spectra (refs. 16 and 17). The success of

this correction technique was limited by the unknown nonlinear effects of the reflecting surfaces and complications due to the highly periodic nature of rotor

signals. However, it was concluded (ref. 15) that the echo contamination can be

partially removed from the measured spectra to yield an improved estimate of the

free-field spectrum. The acoustic spectra presented in this report have been

corrected for the major reflections. Because this technique in its present state

must be applied on a case-by-case basis and typically is only a small correction to

integrated noise levels^ and because of the very large amount of data presented here,

the overall integrated sound metrics (OASPL and BLSPL) have not been corrected for

reflections. The reader should note also that the acoustic time history data presented here are not corrected for acoustic reflections.

Geometric and Acoustic Near-Field

All the microphones employed during this test were located within 4 rotor radii

of the rotor hub. (See table II.) These locations were limited by the physical size

of the tunnel test chamber. Although there is no clear definition of the geometric

near-field of a rotor, the measurements presented here are believed to be in the

geometric near-field of the rotor. The acoustic near-field may be defined relative

to the wave number of the noise source, and it is generally defined by the relation

Kr > 1, where K is the acoustic wave number and r is the distance from source to

receiver. For the first rotor harmonic (100 Hz), the closest microphone locations

(locations 1 and 2) are in the acoustic near-field of the rotor. Above the first

harmonic, all locations can be considered to be in the acoustic far-field.

Refraction

Refraction through the free-jet shear layer is another limiting factor for the

OTS microphone locations. The utility of these locations will be more qualitative

than quantitative in that differences in level for similar velocity conditions can be

assessed. It is possible to predict theoretically the effect of transmission through

a jet shear layer on the measured amplitude and direction of an acoustic signal

(ref. 18). However, this theory assumes that the source is compact. In the case of

a rotor model, the rotor is relatively large compared to the distances to the microphones, and the signal location of origin is not known, making it quite difficult (if

not impossible) to include such a correction to the measured data. Fortunately, the

amplitude and directivity angle corrections are not severe for flow speeds in the

range considered here (Mach number range from 0.06 to 0.12). Because of the aforementioned complications, no shear layer corrections have been applied to the OTS

acoustic data presented herein.
Repeatability

During the test, several conditions were repeated on different days to provide

an assessment of data repeatability. The averaged time histories and spectra of

three microphones for all these repeat runs were compared. In general, the repeatability was quite good. A typical example of the repeatability is given in figure 12, which shows a comparison of the averaged acoustic signal plotted against time

(normalized by 1 rotor period) for two similar test conditions acquired on different

days.

Summary of Data Quality

The microphone locations to be presented here are 1, 2, 3, 4, 5, 7, 8, 9, 12,

and 17. All microphones, except 7 and 8, are located inside the tunnel test section

(ITS). All may be considered to be in the geometric near-field of the source. Most

locations are in the acoustic far-field for frequencies above 300 Hz (the third rotor

harmonic). For the microphone data presented here, in the speed range of 40 to

90 knots, the tunnel background noise is not a serious contaminant. The average

spectra and overall levels (OASPL and BLSPL) are corrected on a squared pressure

basis for the measured background noise. The spectra are also corrected using the

power cepstrum technique for acoustic reflections. The averaged and instantaneous

time history data presented are not corrected in any manner. The effect of shear

layer refraction is contained in the data of locations 7 and 8, although this effect

is judged to be small because of the lower Mach number range tested. The repeatability of the acoustic data has been found to be acceptable.

DISCUSSION

The following discussion is a summary based on the data presented in appendixes A and B. In the following text, only data for the baseline-tip high-twist

rotor and the baseline-tip low-twist rotor are presented. Appendix A presents

comparisons, using two analysis methods, of sound pressure levels plotted against

tip-path-plane angle as a function of forward velocity. (See figs. A1 to A10.) Each

figure shows two different sound pressure level metrics (OASPL and BLSPL) plotted

against rotor tip-path-plane angle for each of the unique rotor configurations (tip

designs shown in fig. 4). Each curve in figure 5 is for a constant tunnel speed.

The shaded symbols represent the OASPL results and the open symbols represent the

BLSPL results. As will be explained subsequently, the BLSPL is believed to be a

useful tool for extracting the BVT impulsive noise from the total rotor noise.

Appendix B presents representative instantaneous time history and average spectral

data for selected test points in appendix A. (See figs. B1 to B10.)

Near-Field Location

Microphone 1 was affixed to the model fuselage and moved with the model through

all its position changes. The microphone coordinates in terms of radial distance r,

polar angle 9, and azimuth angle ty for this microphone are 0.67 m (2.2 ft), 35°,

and 110°, respectively. The trends shown in figure 13 are typical of almost all the

rotor configurations tested. The overall sound pressure level (OASPL) increases consistently with rotor angle, with the highest levels at high tip-path-plane angles.

For the high-twist standard rotors at each rotor angle, the OASPL values are within

5 dB for the range of flight speed. This effect is illustrated by figure 13(a),

10 .
which shows the OASPL and BLSPL trends with flight speed and tip-path-plane angle for

the baseline-tip high-twist rotor. The low-twist rotors exhibit a greater range of

overall sound level at each rotor angle. This effect is illustrated by figure 13(b),

which shows the same data for the baseline-tip low-twist rotor. Here the difference

in sound level is as much as 15 dB at a = 0°. In addition, a comparison of

figures 13(a) and 13(b) shows the OASPL of the low-twist rotors to be more heavily

influenced by the midfrequency acoustic energy (BLSPL) than the high-twist rotors,

particularly for the tip-path-plane angles between 0° and 5°. This effect can also

be observed in the other tip designs for the high-twist and low-twist rotors at microphone 1. (See fig. A1.) The band-limited sound pressure level (BLSPL) increases

with tip-path-plane angle to a maximum for each speed; however, this maximum is at a

different angle for each velocity. This maximum BLSPL occurs at progressively

smaller tip-path-plane angles as the velocity increases. This feature is illustrated

in figure 14, which shows the tip-path-plane angle for maximum BLSPL plotted against

tunnel speed for both baseline rotors at microphone 1. Note that the maximum BLSPL

is at about the same decibel level at each speed.

To investigate the reasons for the two sound metrics in figure 13 to exhibit

differing trends, the narrowband spectra may be examined. Figure 15 shows the narrowband spectra for the 70-knot data (run 106 in fig. 13(a)) of the high-twist

baseline rotor for tip-path-plane angles a from -6° to 8°. Note that the acoustic

level of the fundamental frequency (about 100 Hz), typically 10 dB greater than any

other higher harmonics, begins to increase at a = 0° and reaches a maximum at

a = 10°. Also note that the harmonic levels above 500 Hz also increase, evident at

about a = -2°, and reach a maximum at a = 4°. Not only do the harmonic levels increase to a peak at a = 4°, but also it appears that "sidebands" (multiples of the

shaft frequency) of these harmonics are increasing. This is particularly evident

at a = 0° and 2°. These midfrequency harmonics then decrease as a increases to

8°, as also shown in figure 13(a). These differing trends of the low-frequency blade

passage harmonics and the midfrequency shaft and blade passage harmonics with tippath-plane angle are measured directly by the integrated OASPL and BLSPL values.

To examine further the changes in the spectral content, the averaged time

histories may be examined (fig. 16). The curve in the middle represents the mean

signal, and the upper and lower curves for each test condition represent the standard

deviation about the mean signal. At a = -6° and -4°, the signal is nearly sinusoidal, indicating the dominance of the fundamental frequency. At a = -2°, some evidence of impulsive activity is seen in the waveform. This activity is seen particularly near 0.8 percent of the rotor period, in the "spikey" character of the mean and

standard deviation data. At a = 0° strong impulses are seen in the waveform.

These impulses are very repeatable in both amplitude and phase, as shown by the

standard deviation bands. At a = 2° and 4° the impulsiveness is still seen but appears to have more variability in peak level and location of the impulse in rotor

revolution. At a = 6° there is still some indication of impulsive content, but

at a = 8° the signal again is dominated by the fundamental frequency with no

impulsive content. These changes in the impulsive character are a direct result of

the changing wake geometry, and thus the changing blade-vortex interaction process.

Inspection of figure 13(a) shows that the maximum BLSPL at a tunnel speed of

70 knots (run 106) occurs at a = 4°. However, inspection of the time history curves

of figure 16 could lead to the conclusion that the condition of maximum BVI impulsive

noise occurs at a = 0°. This apparent contradiction is due to the time averaging of

the acoustic signals. Figure 17 displays an instantaneous (unaveraged) time history

for each of the averaged signals of figure 16. A comparison of the averaged and instantaneous signals at a = -6°, -4°, -2°, 0°, and 2° indicates that the averaging

11
process yields a reasonable smoothed estimate of the instantaneous signals while removing random variability and background noise. However, a comparison of the averaged and instantaneous signals at a = 4° (compare figs. 16 and 17) indicates that

the BVI impulses have enough variability in phase that the averaging process "smears"

them out. Although the average time history-of figure 16(f) does not show impulsive

behavior, the standard deviation bands do indicate a significant amplitude variation.

Thus, in this case the averaged time history is not a useful representation of the

actual rotor signal. (However, because of high background noise levels in the data,

the instantaneous time history data are also not considered as a reasonable estimate

of the actual signal.) This variability in the emission time of the BVI impulses is

attributed to variability and instability of the blade-vortex encounter process at

that particular operating condition. Interestingly, this specific test condition was

also the maximum BLSPL condition at 70 knots. It is concluded from these observations that the best available indicator of BVI impulsive noise for this data base is

the acoustic energy or spectral characteristics of the midfrequency bands. Caution

must be exercised when interpreting the BVI noise variation based on the conditional

averaged or instantaneous time history data alone.

Under Flight Path

Microphones 2, 3, 4, and 5 were mounted along the tunnel centerline, ahead of

the rotor, essentially along the flight path. The acoustic data for all the rotor

systems measured at location 2, with (r, 0, iji) coordinates of (1.90 m (6.2 ft), 66°,

162°), show generally the same trends as microphone 1. Two examples of the sound

level trends are shown in figure 18, which shows the OASPL and BLSPL trends for the

baseline high- and low-twist rotor systems. For all the rotor systems, the OASPL is

more dominated by the midfrequency energy (BLSPL), particularly for values of a

between -2° and 6° as shown in figure 18.

The OASPL data of microphone 3, with (r, 9, >J>) coordinates of (2.53 m (8.3 ft),

44°, 184°), show essentially the same trends of increasing sound level with increasing tip-path-plane angle, but the BLSPL values are still quite close to the

OASPL values, especially in the mid-a region (fig. 19). The OASPL values for microphone location 3 show almost a bucket shape for some of the rotor systems (see figs.

A3(b), (d), (e), (f), and (g)), particularly at the lower speeds. The BLSPL curves

still show the peaking of sound level at a progressively decreasing tip-path-plane

angle with increasing flight speed. Note again that the peak BLSPL is at about the

same acoustic level for all the flight speeds.

Microphone 4 (4.27 m (14.0 ft), 13°, 172°) was located quite close to microphone 5 (4.42 m (14.5 ft), 23°, 177°), but closer to the hub (a 3-percent difference

in distance). Although the trends for each location are quite similar, the levels

are generally a little higher at microphone location 5 than at microphone location 4,

even though location 4 is closer to the source. This comparison is seen in figures 20 and 21 . It is not likely that reflections are causing this discrepancy

because the reflections received at each microphone were about the same amplitude.

(See table VI.) Differences in background noise should not be a factor either since

this effect has been corrected from the results shown here. It could be inferred

from these data that the radiation pattern from the lifting rotor must be highly

directional, an effect which may be causing these easily discernible level differences. Another possible explanation is the fact that the microphones are in the

acoustic and geometric near-field. The OASPL values at microphones 4 and 5 are very

much dependent on the BLSPL values, especially for the low-twist models.

12
Above Rotor Disk Plane

Microphone 7 (5.27 m (17.3 ft), -22°, 91°) and microphone 8 (5.88 m (19.3 ft),

-23°, 64°) were located outside the tunnel test section (OTS) and above the rotor on

the advancing side. Microphone 7 data for the baseline high-twist and low-twist

rotors are shown in figure 22, and microphone 8 data are shown in figure 23. Both

locations exhibit a very linear increase in both OASPL and BLSPL with tip-path-plane

angle, but the BLSPL has a steeper slope than the OASPL curves. The BLSPL data for

the low-twist rotors show some of the peaking that is characteristic with a as seen

in the near-field microphone and flight path locations (locations 1, 2, and 3), but

only at the higher speeds. (See the 70- and 80-knot curves of figs. 22(b) and

23(b).)

In Rotor Plane

Microphone 9 was located in the rotor plane at (3.54 m (11.6 ft), -2°, 132°).

The OASPL curves for the high-twist rotors are fairly insensitive to changes in tippath-plane angle (fig. 24(a)). This result is as might be expected from theory

(ref. 19) and experiment (ref. 20), which have shown that the sound levels in the

plane of the rotor are dominated by thickness noise. These levels are a function

only of rotor geometry and tip speed and are not sensitive to loading noise; thus,

they are not a function of rotor load distribution or angle of attack. The OASPL of

the low-twist rotors seems to be more influenced by the midfrequency content (BLSPL)

than the high-twist rotors, especially at the higher speeds (70 to 80 knots). This

effect is reflected by the OASPL data that seem to display the same dependence on

tip-path-plane angle as the BLSPL data (fig. 24(b)).

Advancing Side

Microphone 12 (3.96 m (13.0 ft), 25°, 133°) measured the sideline noise on the

advancing side of the disk at about the same angle below the hub as at microphone 5

(4.42 m (14.5 ft), 23°, 177°). The high-twist OASPL curves appear fairly insensitive

to tip-path-plane angle (fig. 25(a)), whereas the low-twist OASPL curves (fig. 25(b))

show the same steady increase in sound level with tip-path-plane angle seen in the

near-field microphone (location 1). Inspection of all low-twist data for location 12

shows again that the OASPL values of the low-twist systems were more heavily influenced by the midfrequency levels (BLSPL) than the high-twist systems.

Retreating Side

Microphone 17 was located under the retreating side of the rotor at (2.71 m

(8.9 ft), 36°, 270°). The trends of OASPL and BLSPL for all the rotor models are

generally the same, showing an increase for moderate tip-path-plane angles and a

decrease at very small and very large tip-path-plane angles (fig. 26). This dependence of OASPL on tip-path-plane angle is different from that seen at the other locations. The tip-path-plane angle seems to be the most important parameter, with

velocity having a secondary effect. For all the rotors, the BLSPL curves are consistently 10 to 15 dB lower than the OASPL values, showing that the major contribution

to the OASPL is from the first four harmonics.

13
Comparison of Rotor Systems

In general, for the moderate speed range tested, the high-twist levels are relatively insensitive to speed and are more strongly affected by tip-path-plane angle

of attack. The OASPL data for the low-twist rotor at all microphones exhibit more

variability with flight speed than the data for the high-twist rotor. The acoustic

signals of the high-twist rotor are dominated by the first several rotor harmonic

levels. The midfrequency acoustic energy (as indicated by the BLSPL metric) created

by the low-twist systems also seems, in general, to be a larger contributor to the

overall levels than it does for'the high-twist rotors.

The primary difference between the high-twist and low-twist rotors tested during

this experiment is the twist distribution and chord, aside from the tip design between 92 percent radius and the tip. The high-twist blades have -16° of twist and

the low-twist blades have -10° of twist. (See fig. 3{b).) The chord of the hightwist blades was 9.1 cm (3.6 in.) and the chord of the low-twist blades was 7.9 cm

(3.1 in.). Since the low-twist rotor configurations tested exhibited a higher level

of midfrequency acoustic energy than the high-twist rotors at almost every microphone

location considered, it is concluded that the twist distribution and/or chord of the

rotor blade have a greater effect on the midfrequency impulsive noise generated by a

rotor than the tip design.

This conclusion should not be surprising since the twist distribution has an

important effect on the radial loading distribution on the rotor blade surface, and

thus an important effect on the strength and characteristics of the vorticity shed

from the blade. The strength, size, and trajectory of the shed vorticity and tip

vortices are the important parameters for the amplitude levels and impulsive content

of the BVI noise.

Operating Conditions for Minimum Noise Levels

It is well-known that BVI noise is primarily a problem when the rotor is flown

at a moderate forward speed during descent. Inspection of the acoustic data for the

advancing flight path locations (microphone locations 2, 3, 4, 5, and 12) shows that

to minimize the midfrequency acoustic levels in descent, the rotor approach should be

at the highest forward speed and highest descent rate feasible. To minimize the

overall levels in descent, the rotor should be flown at the lowest forward speed and

lowest descent rate feasible. Unfortunately, these two conditions are mutually exclusive. The data presented in this report indicate that for a rotor in descent, the

overall noise levels (dominated by the low-frequency harmonic levels) will be close

to their maximum levels if the minimum midfrequency noise levels are attained.

CONCLUDING REMARKS

A three-phase research program has been jointly undertaken by the Langley

Research Center, the U.S. Army Aer©structures Directorate, and Sikorsky Aircraft to

study the acoustic signals due to the aerodynamic interaction of rotorcraft main

rotors and tail rotors. During the first phase, two different Sikorsky rotor models

with several interchangeable tips were tested in the Langley 4- by 7-Meter Tunnel on

the U.S. Army rotor model system. An extensive acoustic data base was acquired of

the signals generated by these models. The details of the experimental procedure,

acoustic data acquisition, and reduction are documented. Two sound level metrics,

the overall sound pressure level and a midfrequency (500 to 3000 Hz) band-limited

14
sound pressure level, are presented for 10 microphone locations as a function of

flight speed and rotor tip-path-plane angle. The relative importance and trends of

these sound metrics for the two baseline rotor systems are discussed. A more complete set of data for all the rotor configurations tested are presented in the appendixes for the reader's use.

It is shown that the overall sound pressure levels of the high-twist rotor systems are relatively insensitive to flight speed but generally increase with rotor

tip-path-plane angle. The overall sound pressure levels of the high-twist rotors are

dominated by acoustic energy in the low-frequency harmonics, rather than by energy at

a higher frequency. The overall sound levels of the low-twist rotor systems show

more dependence on flight speed, in addition to being quite sensitive to rotor tippath-plane angle. A midfrequency, integrated band-limited sound level, limited by

500 to 3000 Hz, is shown to be a useful metric to quantify the occurrence of bladevortex interaction (BVI) noise. The overall sound levels of the low-twist rotors are

also strongly influenced by the midfrequency noise levels, a result indicating that

the blade-vortex impulsive noise is a more dominant noise source for this rotor

design than for the high-twist rotors. It is proposed that this finding is due to

the different twist distribution and chord of the two rotor systems and that the

different tip shapes have a secondary effect on the midfrequency noise characteristics. The midfrequency acoustic levels for all rotor systems show a strong dependence on tip-path-plane angle. The tip-path-plane angle at which the maximum midfrequency sound level occurs consistently decreases with increasing flight speed.

The maximum midfrequency noise level measured at a given location is constant

regardless of the flight speed.

NASA Langley Research Center

Hampton, VA 23665-5225

April 23, 1986

15
REFERENCES

1. Martin, R. M.; Elliott, J. W.; and Hoad, D. R.: Comparison of Experimental and

Analytical Predictions of Rotor Blade-Vortex Interactions Using Model Scale

Acoustic Data. AIAA-84-2269, Oct. 1984.

2. Egolf, T. Alan; and Landgrebe, Anton J.: Helicopter Rotor Wake Geometry and Its

Influence in Forward Flight.

Volume I - Generalized Wake Geometry and Wake Effect on Rotor Airloads

and Performance. NASA CR-3726, 1983.

Volume II - Wake Geometry Charts. NASA CR-3727, 1983.

3. Shenoy, K. Rajarama: The Role of Scale Models in the Design of "Low BVI Noise"

Rotorcraft. 41st Annual Forum Proceedings, American Helicopter Soc., 1985,

pp. 239-248.

4. Hayden, R. E.; and Wilby, J. P.: Sources, Path, and Concepts for Reduction of

Noise in the Test Section of the NASA Langley 4 x 7m Wind Tunnel. NASA

CR-172446-1, 1984.

5. Sellers, William L., Ill; Applin, Zachary T.; Molloy, John K.; and Gentry, Garl

L., Jr.: Effect of Jet Exit Vanes on Flow Pulsations in an Open-Jet Wind

Tunnel. NASA TM-86299, 1985.

6. Applin, Zachary T.: Flow Improvements in the Circuit of the Langley 4- by

7-Meter Tunnel. NASA TM-85662, 1983.

7. Hoad, Danny R.; and Martin, Ruth M.: Background Noise Measurements From Jet Exit

Vanes Designed To Reduce Flow Pulsations in an Open-Jet Wind Tunnel. NASA

TM-86383, AVSCOM TM 85-B-1, 1985.

8. Martin, Ruth M.; Brooks, Thomas F.; and Hoad, Danny R.: Reduction of Background

Noise Induced by Wind Tunnel Jet Exit Vanes. AIAA J., vol. 23, no. 10, Oct.

1985, pp. 1631-1632.

9. Wilson, John C.: A General Rotor Model System for Wind-Tunnel Investigations.

J. Aircr., vol. 14, no. 7, July 1977, pp. 639-643.

10. Jepson, D.; Moffitt, R.; Hilzinger, K.; and Bissell, J.: Analysis and Correlation of Test Data From an Advanced Technology Rotor System. NASA CR-3714,

1983.

11. Gessow, Alfred; and Myers, Garry C., Jr.: Aerodynamics of the Helicopter.

Macmillan Co., c.1952.

12. Hoad, Danny R.; Elliott, Joe W.; and Orie, Nettie M.: Rotor Performance Characteristics From an Aeroacoustic Helicopter Wind-Tunnel Test Program. NASA

TM-87661, AVSCOM TM 86-B-1, 1986.

13. Heyson, Harry H.: Use of Superposition in Digital Computers To Obtain WindTunnel Interference Factors for Arbitrary Configurations, With Particular

Reference to V/STOL Models. NASA TR R-302, 1969.

14. Yu, James C.; and Abrahamson, A. Louis: Acoustic Treatment of the NASA Langley

4- by 7-Meter Tunnel: A Feasibility Study. NASA TP-2563, 1986.

16
15. Martin, R. M.; and Burley, C. L.: Power Cepstrum Technique With Application to

Model Helicopter Acoustic Data. NASA TP-2586, 1986.

16. Miles, Jeffrey H.; Stevens, Grady H.; and Leininger, Gary G.: Application of

Cepstral Techniques to Ground-Reflection Effects in Measured Acoustic Spectra.

J. Acoust. Soc. America, vol. 61, no. 1, Jan. 1977, pp. 35-38.

17. Syed, A. A.; Brown, J. D.; Oliver, M. J.? and Hills, S. A.: The Cepstrum: A

Viable Method for the Removal of Ground Reflections. J. Sound & Vib., vol. 71,

no. 2, July 22, 1980, pp. 299-313.

18. Amiet, R. K.: Refraction of Sound by a Shear Layer. J. Sound S Vib., vol. 58,

no. 4, June 1978, pp. 467-482.

19. Farassat, F.: Theory of Noise Generation From Moving Bodies With an Application

to Helicopter Rotors. NASA TR R-451, 1975.

20. Schmitz, F. H.; and Yu, Y. H.: Helicopter Impulsive Noise: Theoretical and

Experimental Status. NASA TM-84390, USAAVRADCOM TR 83-A-2, 1983.

17
TABLE I.- DETAILS OF ROTOR MODELS

Hub type ......................... Fully articulated

Number of blades Four

Airfoil section See figure 3(a)

Hinge offset, cm (in.) 7.6 (3.0)

Root cutout, cm (in.):

High-twist rotor. 18.5 (7.3)

Low-twist rotor _ _25_.9_ (Jl 0.2).

Pitch-flap coupling angle, deg -2

Twist See figure 3(b)

Radius, cm (in.):

High-twist rotor 142.8 (56.2)

Low-twist rotor 142.2 (56.0)

Chord, cm (in.):

High-twist rotor 9.1 (3.6)

Low-twist rotor 7.9 (3.1)

18
TABLE II.- MICROPHONE LOCATIONS WITH RESPECT TO MODEL HUB AT ZERO PITCH

Microphone

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

x, m (ft)

0.18 ( 0.6)

.73 ( 2.4)

1.83 ( 6.0)

4.12 (13.5)

4.09 (13.4)

2.35 ( 7.7)

.12 ( .4)

-4.09 (-7.7)

2.39 ( 7.8)

.06 ( .2)

-2.50 (-8.2)

2.44 ( 8.0)

.12 ( .4)

-2.41 (-7.9)

-2.38 (-7.8)

-.88 (-2.9)

0 ( 0)

-.70 (-2.3)

3.75 (12.3)

y, m (ft)

-0.52 ( -1 .7)

-.24 ( -.8)

.15 ( .5)

-.61 ( -2.0)

-.24 ( -.8)

-2.65 ( -8.7)

-4.88 (-16.0)

-4.88 (-16.0)

-2.62 ( -8.6)

-4.88 (-16.0)

-4.79 (-15.7)

-2.65 ( -8.7)

-4.73 (-15.5)

-4.91 (-16.1)

-4.66 (-15.3)

-5.34 (-17.5)

2.20 ( 7.2)

4.88 ( 16.0)

-4.33 (-14.2)

z, m (ft)

-0.40 (-1.3)

-1.74 (-5.7)

-1.74 (-5.7)

-.98 (-3.2)

-1.71 (-5.6)

1.19 ( 3.9)

1 .95 ( 6.4)

2.32 ( 7.6)

.12 ( .4)

.09 ( .3)

.09 ( .3)

-1.68 (-5.5)

-2.01 (-6.6)

-1.95 (-6.4)

-1.74 (-5.7)

-1.04 (-3.4)

-1.62 (-5.3)

-1.07 (-3.5)

.12 ( .4)

r, m (ft)

0.67 ( 2.2)

1.90 ( 6.2)

2.53 ( 8.3)

4.27 (14.0)

4.42 (14.5)

3.75 (12.3)

5.27 (17.3)

5.88 (19.3)

3.54 (11.6)

4.88 (16.0)

5.40 (17.7)

3.96 (13.0)

5.15 (16.9)

5.82 (19.1)

5.52 (18.1)

5.52 (18.1)

2.71 ( 8.9)

5.06 (16.6)

5.73 (18.8)

e,

deg

35

66

44

13

23

-19

-22

-23

-2

-1

-1

25

23

20

18

11

36

12

-1

*,

deg

110

162

184

172

177

132

91

64

132

91

62

133

91

64

297

81

270

278

131

r/R

0.5

1.3

1 .8

3.0

3.1

2.6

3.7

4.1

2.5

3.4

3.8

2.8

3.6

4.1

3.9

3.9

1 .9

3.6

4.0

= 0°

19
TABLE III.- VARIATION IN POLAR ANGLE OF MICROPHONE LOCATIONS DUE TO

CHANGES IN TIP-PATH-PLANE ANGLE

Tip-pathplane angle,

a, deg

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

2

58.33

59.62

60.91

62.20

63.49

64.78

66.07

67.35

68.63

69.90

71 .17

72.42

73.65

74.86

76.04

77.19

78.28

Polar angle, 0, deg, of microphone location -

3

36.34

37.51

38.68

39.86

41 .05

42.24

43.43

44.63

45.84

47.05

48.26

49.48

50.70

51 .93

53.16

54.40

55.64

4

7.08

8.09

9.11

10.12

11 .15

12.17

13.20

14.23

15.26

16.29

17.33

18.37

19.42

20.47

21 .52

22.57

23.63

5

16.32

17.37

18.42

19.47

20.53

21.58

22.64

23.71

24.78

25.85

26.92

27.99

29.07

30.15

31 .24

32.33

33.42

7

-21 .86

-21 .86

-21 .86

-21.85

-21 .83

-21.82

-21 .80

-21.77

-21 .74

-21.71

-21.67

-21.63

-21 .58

-21 .53

-21 .48

-21 .42

-21 .36

8

-20.63

-21.06

-21 .49

-21.92

-22.34

-22.76

-23.17

-23.58

-23.99

-24.39

-24.78

-25.18

-25.56

-25.95

-26.32

-26.69

-27.06

9

-5.97

-5.31

-4.64

-3.97

-3.31

-2.64

-1 .97

-1.31

-.64

.03

.69

1.36

2.02

2.69

3.35

4.01

4.67

12

20.49

21 .24

22.00

22.74

23.48

24.22

24.95

25.68

26.40

27.12 I

27.83

28.53

29.23

29.92

30.60

31.27

31 .93

17

35.97

36.09

36.18

36.26

36.31

36.35

36.36

36.35

36.31

36.26

36.18

36.09

35.97

35.83

35.67

35.49

35.29

TABLE IV.- VARIATION IN RADIAL DISTANCE OF MICROPHONE LOCATIONS DUE TO

CHANGES IN TIP-PATH-PLANE ANGLE

Tip-pathplane angle,

a, deg

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

Radial distance, r, m, of microphone location -

2

1 .94

1.93

1.92

1.92

1.91

1.91

1 .90

1.90

1 .89

1 .89

1 .88

1.88

1 .88

1.87

1 .87

1.87

1 .87

3

2.59

2.58

2.57

2.56

2.55

2.54

2.53

2.52

2.51

2.50

2.49

2.48

2.48

2.47

2.46

2.45

2.44

4

4;35

4.34

4.32

4.31

4.30

4.29

4.27

4.26

4.25

4.24

4.22

4.21

4.20

4.19

4.18

4.16

4.15

5

4.51

4.50

4.48

4.47

4.46

4.45

4.43

4.42

4.41

4.40

4.39

4.38

4.36

4.35

4.34

4.33

4.32

7

5.26

5.26

5.26

5.26

5.26

5.26

5.26

5.25

5.25

5.25

5.25

5.25

5.25

5.25

5.25

5.25

5.25

8

5.86

5.86

5.87

5.87

5.88

5.88

5.89

5.89

5.90

5.90

5.91

5.91

5.92

5.92

5.93

5.93

5.94

9

3.59

3.59

3.58

3.57

3.56

3.55

3.54

3.53

3.52

3.52

3.51

3.50

3.49

3.48

3.47

3.46

3.46

12

4.02

4.02

4.01

4.00

3.99

3.98

3.97

3.97

3.96

3.95

3.94

3.94

3.93

3.92

3.92

3.91

3.90

17

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.73

2.74

20
TABLE V.- VARIATION IN AZIMUTH ANGLE OF MICROPHONE LOCATIONS DUE TO

CHANGES IN TIP-PATH-PLANE ANGLE

Tip-pathplane angle,

o, deg

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

Azimuth angle, i|>, deg, of microphone location -

2

166.12

165.53

164.88

164.17

163.39

162.53

161 .57

160.49

159.28

157.91

156.35

154.57

152.50

150.10

147.28

143.94

139.95

3

184.19

184.28

184.36

184.46

184.55

184.65

184.76

184.88

185.00

185.13

185.27

185.42

185.58

185.75

185.93

186.13

186.34

4

171 .88

171 .83

171 .79

171 .74

171 .69

171 .63

171 .57

171 .51

171 .45

171 .38

171 .30

171 .23

171 .14

171 .06

170.97

170.88

170.78

5

176.77

176.74

176.71

176.68

176.65

176.62

176.58

176.55

176.51

176.47

176.43

176.38

176.33

176.29

176.23

176.18

176.12

7

89.94

90.19

90.44

90.69

90.94

91 .18

91 .43

91 .68

91 .93

92.17

92.42

92.66

92.91

93.15

93.39

93.63

93.87

8

62.87

63.09

63.32

63.55

63.79

64.04

64.30

64.57

64.84

65.12

65.41

65.71

66.02

66.33

66.66

66.99

67.32

9

132.82

132.74

132.65

132.55

132.45

132.33

132.21

132.07

131 .93

131 .78

131 .61

131 .44

131 .26

131 .07

130.87

130.66

130.44

12

135.28

134.87

134.45

134.01

133.56

133.09

132.60

132.10

131 .58

131 .04

130.49

129.92

129.33

128.72

128.09

127.44

126.77

17

263.59

264.65

265.71

266.78

267.85

268.92

269.99

271 .07

272.14

273.21

274.28

275.34

276.40

277.45

278.49

279.53

280.55

21
TABLE VI.- ESTIMATED REFLECTION AMPLITUDES AND DELAY TIMES FROM IMPULSE DATA

Microphone

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

V = 0 knot

At, sec

0.00136

.01000

.00308

.00984

.00248

.024

.00404

.0018

.001

.009

.001

.010

.013

.016

.00075

.009

.013

.0073

.006

.006

.016

.019

.002

.002

.027

.002

.020

.003

.032

.002

.040

.003

.010

.026

.006

A/A0

0.25

.17

.57

.22

'".49

.10

.20

.18

.15

.15

.22

.10

.10

.10

.18

.18

.18

.22

.20

.35

.16

.16

.49

^25

.10

.20

.14

.27

.18

.10

.10

.38

.11

.17

.22

Surfacea

Fuselage

Floor

Floor

? >

Floor

Floor

Mic. stand

Mic. stand

Floor

Mic. stand

7

?

?

?

?

7

7

?

?

?

?

Floor

Mic. stand

?

Mic. stand

Floor

7

Control room

Mic. stand

South wall

?

Floor

Control room

South wall

V = 80 knots

At, sec

0.00116

.01112

.00312

.00992

.00224

.00376

.0019

.002

.009

.009

.013

.0023

.001

.006

.006

.019

.022

.00204

.002

.001

.018

.0015

.019

.004

.025

.003

.003

.011

.0^4

.020

.025

.005

A/AO

0.40

.16

.56

.21

.33

.12

.11

.22

.13

.23

.10

.16

.25

.25

.55

.18

.18

.43

.20

.27

.10

.23

.12

.20

.18

.23

.18

.18

.18

.18

.18

.35

Surface3

Fuselage

Floor

Floor

?

Floor

Floor

Mic. stand

Mic. stand

7

?

?

?

?

7

Floor

Mic. stand

Mic. stand

Floor

?

?

7

Floor

7

?

?

X?

Control room

7

aThe question mark (?) indicates that echo delay time could not be

easily related to an existing surface in test chamber.

22
4-

H

a

<o

e

1

C

3

a

M

r

0

•H

)

4

S

O

3

C

J

1

tf

4J

•H

l

C

3

-0

JS

<D

C

r

Cm

•H

23
24
re

C

§

•O

§

to

c

C

I

n

0

•O

)

VI

0)

3

•H g

O

"2

« 8

5 - S

o g

"I c

'. Q) O

N

 SS

2 " S S S to

25
CoO

«4o—+5CoO

 a

o co

co o>

EE

0 o1 I

IOIO

00

inouE

CO

O)

<*.

y= o

CoOCooOcoo

\*

4Jwa)(B

0•o!

fc•Hd0) CNIo0o
r/R

12.19 .47.50

U- SC1095

SC1095

.82.85 I.93 1.0

SC1095 R8

r/R

.18 .19

SC1013 R8

High-twist rotor

.46 .80.83 .95 1.0

_M* SC10XX R8 *|«- SC1095 R8 -H K SC1095

Low-twist rotor

(a) Rotor blade planform.

Rotor blade

High twist

----Low twist

(b) Rotor blade twist distribution.

Figure 3.- General description showing blade planform, airfoil section, and twist distribution of two rotor models.

27
0.95R

I

STANDARD TIP

0.92R

SWEPT TAPERED

TIP WITH STANDARD

AIRFOIL (SC1095)

0.95R

SWEPT TAPERED

TIP WITH NEW

AIRFOIL (SSC-A07)

PARABOLIC TIP

(SSC-A07)

SQUARE TIP

(a) High-twist tips. (t>) Low-twist tips.

Figure 4.- Geometric description of interchangeable blade tips of rotor models.

28
C

O

LLI C

ULOJ

CKO

CM

CO00

0(Co2T34J -H

ftO

) C§O(OOO•O-H^J•H0n+Jh

•rHX13•H)o23n>

Bap ' Ba

p '

29
(

o

£

0

"35

o o o o o

O> 00 S. CO 1C

fC

•<*

gp '|9A9| ejnssejd punog

0) -P

C -0

-H C

S-i

4J N

o as

0,4*

03 CM

fl) •»

05 cn

••-I

O 0)

C C

0

•O *

c a

3 O

O fc-i

Vt O

CT

1

 -H

1^1 y*

O

o

 C

•-I C

I

EH

o

a

•

1

0)

0

Cn

•H

30
oooo

o>CO

CO

*-•

(1o) CCDCOa(D

o H N. IOoCOo

0)

•

(1o) 0)

ft

® 8 "1§5

•gg 2 § I?S § ^5

i-(05l o

CoO

CMo

OO

0O>

COO

OP 'idsvo

31
1

2O CO

o "1

CD -QCDQ

.

O « co "CD O H- CoO

COo

CMooo

CoD

0o0

f

o(0Soo-p•HI 0)

(1)

CO

CO

+J'o

C§O

0)c

Vo4

« s to S

• go

8P 'IdSVO

iIo£(0H0C30)0n

32
H

fT

T~

o

o

o

i

\Ji

0

CO

O

CO

*oC"

-*

•*

0

•o

)

0

a

)

(0

"5

•

3

c

c

1-

•

o

c

to

rO

O

(0

4->

•H

t

i-

>

(

<1)

0

iH

)

CO

Q

4J

C

0

•H

)

DI

Vi

fll

•O

/

0

00

•

1

o

o

o

1-1

s*S

)

tj

C

3

M

n

fo

•H

I I I I I I I I I I 1C

o

CO

o

C

o

O CM

o

o

o

O

o

) 0

o

0

EC

8P 'IdSVO

33
H o

•rcnl

c «.p

^ o

a

CO

8,

o

4J

in

o

0

•g

 h

2 d

'o ^

S 0

C

tn

1

gp '|8Aa| ajnssejd punog

34
o

<

>»

<

<D*

i_

3

(0

0)

k.

a

•o

1

" j f*D\rec\ wave

8 —

.6-

•

4

.2

-.2

-•6

-.8

1 0 I I I

/Echo from fuselage ( At <=» 0.001 sec)

ji {* Echo from floor (At%0.01 sec)

i

I^T^. ^ ^^^^^,

\

I I . I 1 1 I . 1

.49 .51 .53 .55 .57 .59 .61

Time, sec

(a) Microphone 1.

1.0 -

<

oT

0)

.6

.4

.0

-.4

• Direct wave

•Echo from floor (At^0.002sec)

(At%0.024sec)

.48 .50 .52 .54 .56 .58 .60 .62

Time, sec

(b) Microphone 3.

Figure 10.- Examples of impulsive source calibration data

with acoustic reflections. V = 0 knot.

35
<

D

CO

Q)

•HOM

I

OOOOI-PO

0O)

COtCMOCOO

OO

TK- OOCOo

0

I)

ITOOI

ffiNO)O•a

-Jo

iq

0-P

•rHO] U§

V/V

(CIto4JU1COc-o

£ oe3wX(C

ttn

36
CO

CO

CM

m

o

o

1

m

o

1

CM

1 -— I

J

0 0

i

CN

in

1

in

o

o

_j 0

h

m

0

i

-

0

CO

4J

o

)

CO

•

in•

Tl

Q

0

*iZ

.0

W

.

0 •

•H 0

.p *Jen

3 II

8 a

<c

-a ^

0) CO

CP+J

(0 O

h C

ft\ IS W r*i

«j O

r0

iw

 II

1C 4)

+J C

(3 O

ft ft

0) O

M V4

O

M-l -H

0 S

(0

CN

-tuo/seuAp '

o

37
a: COO

c/m> Q_

c/)

O CM 10 N

O O O O O O O O in to [-- oo

0) o _

 cD

CM Q. ' I

•* JI

I +O>

(D Q_ 1

 I

00 Q.

10

SG

-Htr*I•HCO 4JCO 4Jmc-o(C

fc•O+J •Ha

cn

00 0)

T)

co „

_Q) ca

CN°

(D

°!

CM Q.

D

CO Q_ 1

 I

00 Q.

toO

CM

in

CMO

om

Ol

O

a "~

•H 0)

•P Co C M o o

•H -H

•P E (0O

 CO

4-1

t» O

10 CX

CO H O0) 00 0) O H 4J Oi O M in g•H

 8

a•a1 -p-H C

T

e c

-H (0a)

•a >i c -P

Ifl -H

^3 OO •d rH § ? H 0) Id > H O :

(!)

O)

ro

(0C

gp '|8A9| punos

38
O i- «- CM O IO

O O fO O ro O

CM CM CM CM CM CN

Z

o

 o o m o in o i

\s in CD ID i"*- I

s

- oo

 L

-

ft onO O

DQ

Q_

Q

ro CM

m

CM

o m

o

m

gp 'pA9| djnsssjd punos

Q)

_D

CM Q_

' I

* _C

I -

D

M

10 Q,

 I

1

00 Q.

cn

o

.

o

CO

CM

_g

CM Q.

^f_C

I +->

O

(O Q_

00 Q.

O

o 1

o

5

+J

(0

•o

_ ^3

cn ~

(D

D

c

TJ

0)

C

H

•O

J

I

CJ

O

•

0

fO

1

V4

D

3

l

fc

•H

39
O)

CD

TJ

Q_

CO

_J

QQ

E

D

'x

CO

12 r—

10

8

6

4

2

0

-2

-4

40

O Low-twist rotor

D High-twist rotor

50 60 70 80

Tunnel speed, knots

90

Figure 14.- Tip-path-plane angle for maximum band-limited sound pressure level

plotted against tunnel speed for high- and low-twist baseline rotors for

microphone 1.

40
CD

•o

"55

CD

V)

V)

1

o

CO

115-

105 r95

85

75 l_L

(a) d=-6

(c)a=-2°.

1 OOO 2OOO 3OOO

Frequency, kHz

4OOO 5OOO

Figure 15.- Averaged narrowband spectra for high-twist standard tip at 70 knots,

over range of tip-path-plane angle. Microphone 1; run 106.

41
CO

0)

0

(0

0)

o

CO

(d)a=0°.

1 OOO 2OOO 3OOO

Frequency, kHz

Figure 15*- Continued.

4-OOO 5OOO

42
CO

•o

w

0)

o>

(0

0)

0)

o

CO

85

75

(g)a=6

-co

1 OOO 2OOO 3OOO

Frequency, kHz

Figure 15.- Concluded.

4-OOO 5OOO

43
1500

75O

CM

o

"35CD

£

CO

CO

CD

a

o

-750

-1 5OO

15OO

<a)a=-6°.

75O

-750

CO

o-15OO

o

< 150O

75O

(b)a=-4°.

-750

-1500

(c)a=-2°.

_L _L _L

.1 .2 .3 .A- .5 .6

Period

.7 .8 .9 1.0

Figure 16.- Averaged time histories for high-twist standard tip at 70 knots over

range of tip-path-plane angle. Middle curve is mean time history; upper and

lower curves represent standard deviation about the mean; microphone 1;

run 106.

44
15OO

-750 -

-15OO

.1 .2 .3 .4 .5 .6

Period

.9 1 .0

Figure 16.- Continued.

45
150O

75O

CM

o

^.

(0

0)

-750

0)

5-15OO

1 5OO

CD

Q.

J

O2 750

O

O

-75O

-150O

(g) 0=6°.

(h)a=8°.

.1 .2 .3 .4- .5 .6

Period

,7 .8 .9 1.0

Figure 16.- Concluded.

46
15OO

750

CM

O

<D

§

(0

CO

CD

O

1

O

O

-75O

-15OO

15OO

750

\^^\^

(a)a=-6°.

j :—L J I 1 L

-75O

•15OO

15OO

75O

*»J*««>^^

(b)a=-4°.

I I

-75O

-15OO

(c)a=-2°.

.1 .2 .3 .4- .5 .6 .7 .8 .9 1 .O

Period

Figure 17.- Instantaneous time histories for high-twist standard tip at 70 knots

for range of rotor angle of attack. Microphone 1; run 106.

47
1 5OO

75O

CM

O

"(0

0

I

<D

-75O

-15OO

15OO

75O

(d)a=0°.

0)

0.

O

I

O

O

-75O

(e)a=2°.

-750 -

-15OO

I I

.1 .2. .3 .4- .5 .6

Period

.7 .8 .9 1.O

Figure 17.- Continued.

48
1 50O

750 -

O

CD

CDi_

CO

CO

O

-75O

-1 5OO

15OO

(g)a=6°.

_l I L

~ 75O

CO

§

< o

•750

-15OO

(h)a=8°.

j_

.2 .3

J_

.4- .5 .6

Period

.8 .9 1.O

Figure 17.- Concluded.
—

, O CM (O N

0000

Zo o o o o

\^ to CD r^ oo

OnO<l CDQ. C§O

_D

CN Q. 1

 I ^ J

I I •+->o

co a 00 Q. CPen0oc) I +D> ?f CO Q.

CI4J(0•oaP

ffi •H

O 1O O 10 O lO

CN T- r- O O 0)

T- r- «— r— r-

gp '|OA9| ajnss0jd punos

oi

0)

C

C O O £ •* a

4-> 0 U to c o 3 -H m c 10

 g

W IW

(C

w

W 4->

r-! 0

S.S

cu

rl OCO 0) _ S BCMO

 O

0) ITI

•a

to

 M

o3 a)

w DI

•a 1)

<u 1-1

4-1

-H >i

S 4J

•H -H

^H O I O

-O rH

c <u

(0 >

•g n («Overal O CM•Htn3^to

50
—) O i- r- CM O rO

—! o o n o cv o

C£ CM CM CM CM <N CM

O

o o m o m o

10 (D (0 r- I"- 00

o

m

OnO<l

'

8* -

1 I 1 1 1

&x = AV/ \^

D

CO Q.

' 1

00 Q.

0^

T

O

1

 —

Q)

oo (D

TJ

CO .

(D

•

04

(0

B

4J

•H

to

+J

CO

I

•o

^

O

4J

•H

Figur

e 18.- Concluded.

\

CJi

C

O

.C

(D

C

L

D

to

00 Q.

CM

o

o

m

o

o

0)

m

O

O

)

gp '|8A8| sjnssajd punog

51
—, O C

M <O N

—? O O O O 2O

 o o o o

\^ m «o N oo

OnO<l _mi Q_ CO

CM

m

OmOoOm)

D

?f 00 Q

.

T—OI

cn

oo (D"D

ID « Q) ^ c0)cn O

 C

_D

CM CL

1

 I I +-

• D

CD CL

op Q.

1'h-

o\

0)

Ci-Pw-u(0c•c•Cn

c o 0

 -S

•H a -p o u ^ c o 3 -H

Ul g 01<0 g

OT

c-p

>

tt)

 X

0)

,H O00 <^U

 O 3 -P <nin

 o

<u m

4(UT3mO3£J1iH•He•H

U-(

0)>

J-l (0ctp

4-1oo•H

and band

over vel

•era 0)3

gp '|9Aa| ajnssajd punog

52
—, O t- i- CM O K)

-J o o n o n o

01 CM CM CM CM (N CM

o

o o m o m o

in v> co N ts oo

^

CM n

O

(0

00 Q_

_

m

i

Q.

o

Jl

cn

co (D

T)

(0 «

cn

Q

c

)

°l

CM Q.

' I

^ JC

I -

O

M

CD Q_

' I

00 Q.

C

O

M

m

O

o m o I

B

•H

w

ca

4->

03

•s

(d

•o

+J

•H

a

0

•a

)

r3

•a

l

o

O

O

^

3

 fe

gp *|8Aa) ajnssajd

53
D

O CM CO t^

_ O O O O Zo

 o o o o

\£ m CD r- oo

OSQ

CM Q.

I •*-• D

(D Q_ ' I 03 Q_

*

\i\%; ' 1 1 1 o o in r- O gp '|8A9

—

\1*1 1 1

en

oo (D

TJ

(0 .

_0)

Tj- CPc

C M°0) °l CM Q

. ' 1

•* j:

1 -4-

1 D

(0 Q_ ' | 00 Q. 0^

o m o m 1 o o> en oo 1 ajnssajd punog

(- •O1<c

4-toJJ(0•o) CO

ffi -H

C O o ^ •H ft 4J O o ^ c o 3 - 0H (0 t-l to +Jw H O 0) C > ^ 0)

il O00 0M)

 O

3 -P

01o) o 0) ID OM

 0)

03 tPC

T) OJ (U M 4J •H >

,

B -P

•r4 -H

rH O I O T) rH C <D a > c > inera

 o

CoCPN•H

54
-} o i- i- CM o to

-> o o to o to o

OL CM CM W CM CM CM

Z

O

 o o in o in o i

Y m <o <o r~ r-> oo

 L

OaO<]

O

CL

_j

m

o

m oo

O

in

) en

o

CM Q.

I i

.

I -

D

M

CD Q.

' I

€0 Q.

D1

oo 0)

T>

ID .

CM Q.

' I

-* -C

I -4-*

D

co a

' I

00 Q.

mi

oo

O

•H

CO

4J

CO

I

as

•d

+J

•H

3

•o

(D

•a

e

3

(N

o

I

O

rH

n

~ fe

.Q

gp '|8A8| ojnssajd punos

55
-x

z

 O CM CO N

-J O O O O

UL «-«-«-» -

Z

o

 o o o o

in CD N oo

CD

ODO<I

g

o in o

r- O O

in o

Ok 0)

M a

I i

(

'

0

CD

oo 0)

T3

co .

Q

0

C

)

to a

1

 I

ml

GO

+

id

C

•c

(0

M

•o

j

n)

4J

m

O £

•H U

-P O

(

O

2

°°

0)

W o

O (D

en tr>

•O nj

Oj M

•a i? •H -H

•H O

I o

T

C

'O

) 4)

10 o

gp '|aA8| ajnssajd punos

•H

fr.

D

I

56
— i O »- «

T-J O O O

CC « M CM

Z o o o

\ in <o i^

OaO

_

m

j

Q_

CO

O

in

O

in

O

o

O

in

> 0

o

)

III -*J

D

* Q.

' I

oo Q.

00 Q)

"O

<D

Q)

0)

7?

to o

00 Q.

IP

ml

CO

•H

en

-P

en s

•o

(0

•O

•rH

a

0

•C

)

0

tN

u

O

U

tH

3

•a

)

O

^

i

fa

•H

gp 'pA9| ajnssajd punog

57
—. O CM CO f-

-> O O O O

Ql ,- ,- r- ,-

C

o

O

Z o o o o

\£ in to r- oo

CM Q_

D

CD a

CO QL

0

P

r

I

-

ft

*o

(0

T3

•H

•H g

m ^

.8 ^

0)

m

OnO<I

§•••«

o

(0

_^ +J

•N , O to

Tk

aT

 n

 :

•i* \ —

\ \ n V

l ^^4 — w r \

\ i V L •^•^ _ A B

v

^

1 1 1 I 1

»- -

»

H

cn -P

oo CD J.

"° -d

CD .

 K

® 7

•* cn "

c

CN°

(D

~

D

CM Q_

' 1

* £.

1 -

O

M

CD CI

1 ,

1

CO Q.

iP

D m o m o m ol

O O O) 0) 03 CO

isC

W

O

 r^ «id-limite

d soun

d pi sLocit

y rang

e fro

m

5 <u

5

^

 >

« cS

•eiHH

•

o

>

0)

^4

1C

CN

<

C

3

IJ

0)

N

n

gp ajnssojd punos

58
o i- «- CN o n

o o to o fo o

CN CN CN CN CN CM

Z

o

 o o m o m o i

x/incocor^h-o o

 L

CL

_

m

J

_i

Q.

O

OnO<

O

m

O

o

0)

m

0

o

) CO

m

gp '|aAa| ajnssajd punos

CN Q_

' I

^ _C

I -

D

M

co a

' I

00 Q_

cn

CO Q)

TJ

co .

cn

o

c

CM

Q)

^0

CM Q.

' I

•*J

O

I

co a

' I

00 Q.

O

o 1

00

T3

0)

S

•D }~

•O

l

(C

CO

co

4J

m

•O

 (si

'! :

8 e.

59
—j O (N CO

o:

O O O O

Z

O

 o o o o

>£ m CD I

s

- oo

On<C><]

CD

a.

(ft

CN~Q_

I -4--

D

co a

' I

CO Q.

^*i> If 1

op a ,

F w O CM

Dinoinomo l 2

-OO(3)O)COO O 3

a)

D

c

gp '|9A8| ajnssajd punog

a

%

(0

cn

oo (U

CO

(D

4

1

J

C7>

(0

ffi

•H

)-

s

<

S*-< ii i

3 ^

**

TI C

5 5

60
—> O r- r- CM O K)

r^ O O fO O to O

01 CM CN N CM CN IN

Z

O

 o o in o m o i

\x in CD CD 1^ h- 00

 L

Ono<

_

m

j

CL

o

o

m

o

o

o>

m

o>

o

CO

m

CN Q.

I i

D

•DQ.

00 Q.

o

p

00 0)

(

c

0

,

_0)

cn

Q

o

c

)

CM Q.

'

O

CD Q_

00 Q.

ol

00

a

•H

ca

•a

(0

•a

•H

a

T

0)

>

T

o

o

C

O

J

C

3

!M

0)

M

gp ajnssajd punog

61
—j O CM CO

on

C

o

O

o o o o

o o o o

in CD N oo

OnO<1

CL

C

<

O

o

in o m o

<- r- o o 01

in

O

o

5

CM Q.

' I

I •+->

D

CO Q_

1

 I. .

c? Q. -3*

I *~— \

%

O *0

7 * I -

CO

4J

(0

a

10 I

00

gh-twist

cn

co (D

TJ

CD » a3

_Q) _

Tf cn 5

^

c

CM Q.

' I

•* -C

I -

D

M

co a

' I

co^Q.

If

CO

<D

rH

«H

gp 'jaAai punos

T?5 ! Over

a

0)

Vl

fc

-H

3

62
—v O «- «- CM O fO —j o o r> o >o o

C£ CM CM CM CM (N OJ

Z

o

 o o m o m o i

^ m CD <o r-- N to

 L

OnO<l

g

m

j •••<*•

O

m

O

m

O

o

0

m

) 0

o

)

O

00

(D

 Q.

O

cn

CO Q)

(0

C

Q)

D

_

D

I

a

D

(O Q_

' I

00 Q.

O^

in 1

'00

Ck

n

u

•a

4J

•H

)

a

•O

)

+J

en

!

5

to

•P

0)

c§

O

i-l

3

•a

gp '|SA9| ajnssajd punos

63
—

, O CM CD N

—J O O O O

CoOZ o o o o \^ m CD N o

o

OnO<l CDCLSin

CNo in8P

om

oo

Om)

CM Q.

co n ' I

00 Q.

cn

00 0)

CN

(D

J)cnQoc)

CM Q. ' 0

ID Q_ 00 Q_ oi 0)

ftCI•O?4J •HO 4JCO i3-H

c c o o

3-a

o o C M S OOM CO CO rH JJ a) oo 0) CO 3 q co -P CO0) O •O 0 C H 10o

 <1>

T3 C 0) 10 1 ) t l

•35 •H-

ll -H

I O

•o o C r-1 nj <u XI > •O U C 0) * cS

ll

,-iJ

(tf1

sjnssajd punog

Ove •HsCNin

64
—. O »- T- CM O (O

—' O O ro O n O

Q. CM CM CM CM CM CM

CO

hZ

o

 o o m o m o

\x if) (0 ID !"•>• f^ 00

m

OaO<l

CM Q.

' I

* -C

I -

D

M

(0 CL

oo n_

DI

oo (U

TJ

(0 .

cn

D

C

c,

0

°l

CM Q.

CO Q_

' I

00 Q.

Q,

a

•a

(0

4J

•H

)

J

(0

J

+

w

J

I

B

•H CN

If)

o

O

O

3

•a

0)

•o

CM

O

o

m

o

o

cn

m

cn

o

gp *|aA8| ajnssajd punos

65
—

, O (N CD N

-J O O O O UL t- «- «- «-

17) ZO

 o o o o

\X 10 CD h- 03

OaO<l Qm. CO

oto

oo

0m)

0o)

aO

00 Q. oo 0) co .Q) CM Q. ' I

-+.CI •+

>

D

co n 1

 I

00 Q.

Omi oo

ft

S- •c-P•Hl &s•HCO -p10C

0)

C C o o •p ft o o C l-l 3 O"s W O (0 ><-i co to rH -P

tt) O > C 0) X H o 0) 00 3 O CO -P CO0) O

ii in •o o C ^ coo

 cv

•C C CU 10 +J M e•H

 >i

-H 4J

ll -^ I O

•§3

5 5 •§ i < > 0CNVOIo) •H3

gp

 4

|aA9| ajnssajd punoc;

66
D

o i- «- es o n

o o n o r*> o

CM CN CN CM CN

o o in o 10 o i

in co ID ^ N oo

 L

OnO<]

g

m

0

o

m o

o

o>

m

0

o

)

gp '|8A8| ajnsssjd punos

cn

CD 0)

T>

co .

0)

CN Q.

'

O

« a

1

 I

«0 Q.

ml

00

T

M

)

(0

T3

(0

+J

0}

cn

-P

I

U

•a

<D

•o

67
APPENDIX A

COMPARISON OF OVERALL .ACOUSTIC LEVELS FROM TWO ANALYSIS METHODS

The figures presented in this appendix show two sound metrics plotted against

tip-path-plane angle as a function of forward velocity. Each figure presents two

metrics (OASPL and BLSPL) for each of the unique rotor configurations shown in figure 4. Each curve in the figure is for a constant velocity. The solid symbols

represent the OASPL data and the open symbols represent the BLSPL data. The plots

for each microphone are made to the same decibel range, and all the plots are made

with the same scale of decibels per major division to aid in cross comparisons. Each

figure includes nine plots, one for each rotor configuration.

Because of problems encountered during either data acquisition or reduction,

there is a paucity of data for the following: microphones 2, 4, and 7 for the hightwist swept tapered tip with the new airfoil (500-series runs), and microphone 17 for

the high-twist parabolic tip (700-series runs) and the low-twist tapered and square

tips (800- and 900-series runs).

The data base presented here may be furnished to interested researchers in the

form of a computer listing or on digital tape by contacting the authors.

68
O

CO

O

o o o o in <o t^ oo

j/_j OaO<l DsO

CM Q. ' I

*.C

I -

DM

CD Q_ ' I

00 Q. en

oo 0)

~o

co . CM (D0C CM Q

. ' I

co a ' I 00 Q

.

C

•HCO(0T3m4J

•rHaP

ffi •H

•H 0)

•P Co

<w .c

o ao c u o o

•rH -i-l •P S c0

 n

s o

U-l <W m co

4->

to o

(0 Cx ca

iH O 0) 00 CD O

1-1 -p

cu o

CO IT) o•H

 e

c 5

fc

•O 14-1

0!

-p CU

•H (0

•H 1-1

•a >i c -P (0 -H xi oo T3 rH c cu (C > C5UC<U C>UO

CMmCMoom

ol

o

gp '|aA8| ajnssajd punos

69
o <- CM

Z

o

 o o o o o

\^ m CD S I

s

- oo

QaO<] a

_

m

i

Q.

O

ro CM

in

CM

o m

O

m

CM Q_

' I

* _

D

C

CD f)

I i

00 Q.

00 (D

T)

(D .

_Q)

0

C

CM~Q_

' I

I

(0

Q

D

.

O

o I

O

&

•O

ft

w

o

o

<n

in

O

•H twist swept

53

0

U

O

•H

3

•o

)

•itn

s

h

(

fc

gp '|9A8| ajnssajd punog

70
in ID N o o

o o o o «-

m in m m m

0

O

0

Z o o o o o

\s in co N i^ oo

m\ \ m

^

m

o in o

IO CM CM

o m

«- o

CM Q_

' .1

^ -C

I -tD>

CO Q_

00 Q_

cn

CO Q)

CO

cn

Q

c

)

Q.

1

_

D

c

CO Q_

 I

1

00 Q.

o

o

MO

•H

l

•o

w

w

o

r-

(0

•H

M

' cu

CO

4J

(0

£

a

-p

T!

0)

O

O

4J

•H

S i

gp '|8Aa| ajnssajd punog

71
—1 •* co in iv oo

jri .O O O O O

ir fx fx. PX ps. |x,

Z

O

(A

 o o o o o

\s m m to iv oo

(/

>

m

)

\

#

\

\

 \

4

o m o i n o i n

K) CN CM <- r- O

*— r— r~ t— *— t—

gp *|9Aa| ajnssajd punog

CM Q.

O

CO Q,

00 Q.

,

0

 O

0 0)

CD «

-* CD

c

C N

0

Q)

o

 c

_g

CM Q.

' I

^ JI

I -f1

O

00 Q.

o

o 1

O

X

ft

(0

^

(0

XI

O

rH

•H

o

-P

•H

a

I

•^

T3

(1)

§

o

o

C

-P

•H

CO _

•H ^

fe

•H

72
—, o i- r- CM o ro

r: o o ro o n o

C£ CM CM CM CM CM CM

Z

O

 o o m o m o i

\^ if) CO ID f^- N 00

CL

DQ

_j

CL

O

OnO<l

10

o

m o

CM CM

o m

<- o

'3 =

<° Q- £ i

CX) Q.

ro

Q)

CM Q.

' I

-* JZ

I •*->

D

CO Q_

' I

00 Q_

+J

•H

a

o S

"- -O

CP £

"-S ;

10

 " H

(D '* — -P

ol

o

T

3

Q)

3

fa

o

o

c

4J

•H

gp *|8Aa| ajnssajd punos

73
•* in (o

o o o

to to n

o o o

m CD N

ODO

CD

Q.

i

to CN

m

C

o

N

m m

CN Q_

' I

t11

I -

D

M

* Q.

' I

00 Q.

IP

cn

00 Q)

CO

CH

(D

c

o

^

 c

5

CN Q.

D

0

c

0 Q_

ol

O

>-

10

4-1

•H

a

l

x:

(0

4->

CO

i

B

-H

14-1

fa

•H

a

O

4->

•H

I

gp '|aA8| ajnssajd punog

74
— . T

f m co N

-J o o o o

ft! co CD co <o

Z5 o o o o ID ID N CO

_>J

OQO<I DD_j 0. O

o m o IO CM CM

om

Q.

"t JI I •*-O>

co n 1

 I

00 Q_ e ir-

;i=n

CO Q)

TJ

(O . CM 0) CM Q

.

I I I *-D>

CO Q. 1

 I

CO Q_

ol

o

ca

-P

0•o)IOO+J•H3

II a <,Pu •H

gp '

75
-t m co N oo

o o o o o

oo co oo oo oo

£/)

I -

D

^

10 Q_

00 Q.

0)

(0 Q_

' I

00 Q.

n

O U)

M CM

0 in inOol

O

gp *|8Aa| ajnssajd punog

4J

•H

ZOOOO O | I 1 I 1 1

\S in <u r^ CD oo ' .

t—

0

\

^*

^>

^^ 0 — * B^v^

S)OnO<]^ ] 1^ —} ^^^

CQ iV \ _

_j *k % Q- i r\ \

^f ^^^^ B * ^H

o \ \ \

.-,

CT

00 0)

T)

(D «

<I)

n

C

•

Q

0

)

V4

<

a

D

•i1

4J

CO

—

^q

g

•H

 «

£

fa

•H

tr

M

"*

^*

•

1

u

O

C

+J

-H

P
— . in (0 N oo

o o o o

o> 0) en o>

Z

6

 o o o o

\ IO <0 1^ 00

g

OQ

w

K

o

)

IT)

CM C

O

M

1

o

0

gp '|9A8| ajnssajd punog

' I

D

<0 Q.

1

 I

T.9- *

O

D

(0

1

CO

en

00 0)

(0 .

0)

CM Q_

10 O

 I

1

CO Q.

IP

oi

o

4-)

(0

s

s

•H

T

u

0

o

0)

3

77
—. O CM CD N

-J O O O O

Lt t- r- t- »-

C/)

Z

o

 o o o o

v in CD i^ oo

O

CO Q_

oo CL

00

_ tr

ft

>

•H

2 &

B °

§ 4J u-i s

0

C

g

D

CN

o

o

m

o

o

0)

m

gp *|8A8| ajnssajd punog

00 0)

co .

*"5

C

l

(D

CN Q.

' 1

D

<? Q.

' 1 •

o? a

cn

o

«S

co

•p

(C

•s

VJ

co

•o »

5band- 2locit

•H

tn

3

M

0)

o

81

M

(0

rH

H

-78
O r- (M

C

O

O

o o o o

in CD r-- oo

8j.OnO«

CO

o_

m

o m o m o m CM T- r- O O O)

gp '|3A9| ajnssajd punos

' I

•* JI

I -

O

M

CD Q_

' I

f.9- 5 1

 I

e

 W

n

oo (D

T)

co .

Q)

°o

CM Q.

' I

-* .c

I -

o

M

CO Q_

1

 I

00 Q_

O

oi

0)

(0

a

o

o>

in

0

•o

-P

•H

a

)

X

-H

3

•H

CO

-P

4-

•H

C

3

O

>

I

U

•

<N

PL

•H

4

79
c/)

Q

OQ

z

o

.

S

(A

o _

o2

 ~

—

1

CM Q. 

1 i ""I

| -|_> Vj

1 f^

o

!"= i « — *•* i

5 3 ^ c

o

— 1

~^~

—

Q)

15

_

o

>

g

 _

"o

£

 —

0

-Q

 —

^

—

1

U)

2

o) | a

00 Q) ^ «

Q) S,

ID . S ?

0)

 w

 fe

— -p

C '^

CM

0

 V

Q) 0>

o c S

.0 _

CM Q. 3

1 i

' 1

•* JI

1 -

O

M

<D Q_

1 I

1

oo QL

D m o m o m ol

M r- r- O O O) 0)

gp '|aA8| ajnssajd punog

80
•* (o m N oo

o o o o o

Z o o o o o

\^ m in (D ("•» oo

(/;

m

CM

o m o m o

r- O O 01

m

gp '|8A8| Bjnssdjd punog

CM Q_

' I

* JI

I -+-

1

D

« a

00 Q.

01

00 0)

T)

(0 .

0)

CM Q_

O

CO

oo a

O

ol

0)

ft

O

^J

•H

a

•rH

ft

(0

X5

O

iH

•H

C

3

CM

i

a

o

c

0)

•o

P

•H

81
O T- r- CM O rO

o o n o ro o

CM CM CM CM CM CM

2

o

 o o m o m o

\£ in CD co r-- h- oo

>

OnO<]

DO

CL

0

s

1

\

CM Q_

'

D ~

Q- £

CO

00 Q_

1 1 1 1 1 1

1

o

•

— ,0

X*

.£K.

t—

en

00 0)

TJ

CO ...

14-

-H

1

Pi

0

c

•o

(0

*o

•u

-H

5

01

-P

to

-U

•H

0

•O

)

,

0

O

C

+J

•H

C

•

(1)

fe

•H

P

II

• «i

—

1 1 1

C

1

O

0

o

0

D in o m o in o 1

M T- T- O O Cft O)

Q

|

D

_

H

CM

? i C o

D '*

(D 5

gp '|8A8| ajnssajd punog

82
•* m co

O O O

ro n ro

Z

o

 o o o

v m co I

s

-

Si OnO

D

8

Q

•4

CM

O

o

m

o

o

0)

m

' I

I -

0

M

CO Q_

00 Q.

en

00 0)

T>

co .

CN

CN Q.

' I

-* SL

co Q_

' I

00 Q_

CD

o

I

-H

(0

+J

(0

1

•o

.p

•H

C ~

Q

O

)

0)

C

D

«N

C§

+J

-H

C

3

n

gp '|8A8| ajnssajd punos

83
(f)

•z

O

.

(0 N

O O

tO (0

O O

N 80

c/j on

OQ

Q.

58O

CM

10

O

m

O

o

0)

in

' I

•* SI

I -4--

0

CO Q_

1

 I

00 Q.

cn

00 Q)

"D

CM Q_

' I

00 Q.

o 1

O)

ft

-P

Q) 5

0)

iI

+J

•H

c

0)

•o

i

•rH

£

gp '|aA8| Gjnssajd punog

84
—. •* m ID N oo

;-! O O O O O

Q^ CO CO 00 00 00

Z

o

 o o o o o

>y m (O S 00 00

OaO<l

o

Q_

_J

m

CM Q.

Q

o

.

00 Q.

IP

.

- D

0

•o

<

)

<v

(

ft

0

+J

01

oo (D

T)

(O .

*"6

0)

c

>

°J

CM Q

C

O

L

00 Q.

4J

CO

•r-t

0

•O

)

C

<

CM

o

o

4J

•H

c

P

CM

10

O

in

O

o

0

m

)

o 1

O>

*|aA9| ajnsssjd punos

85
m ID N oo

o o o o

o> o> o> <n

C

o

O

Z o o o o

•y in (D I

s

- 00

Q

m

_

_j

CL

O

OaO<

m

O

m

O

o

01

m

gp '|8Aa| ajnssajd punos

CM Q.

CD

D

00 Q)

"0

CD .

0)

CN

 w

0)

O C

D

t£

<° S

o 1

0)

0

ft

)

(-1

&

(0

a

I

.

86
—, O CN CD N

2 2 2 ° 2

Z

o

 o o o o

v m <o r^ to

OaO<l

DQ

_i

a.

10

o m o m o in

CN T- ^ O O 0)

gp '|8A8| ajnssajd punog

Ha

D

*

D

CD

00 Q_

cn

00 0)

(0

_0)

cn

C

CN Q. 1

C

D

L

oi

0)

•

*-*•

«r— *

<a

^•

CT

1

.,_{

>4H

04

0"

£

4->

s

•H

CO

+J

CO

.p

(0

C

•O

<0

•0

4J

•H

*

(0

jr-^

cd

•H

O V

C

C 0

0 f.

•H ft

4J 0

O U

C O

3 -H li i C

m >

o

H

0) <4H

(0

(0

to -P

r-H O

0) C

0)

rH 0

00

0)

Vj O

3 -P

to

to

 o

a) m

tt E

T) K

C '•H

O

3

 0)

CO O>

c

•a (fl

a) V4

*j

-H >i

e -P •rH -H

rH O

1 0

•O rH

C 0)

5

 >

i-l

•a cu

c >

(0

i

 O

r^

r

(0

rH

l

0)

t

ro

i

0

>

r

PK

•H

87
O *- CM

CO

I

Z

o

-

 o o o o o

\^- m (o N N oo

Q_

QQ

_j

Q_

CO

OnO<l

CM

O m

o

m oo

0)

m

gp '|8A8| ajnssajd punos

CN Q.

D

(D a

1

 I

00 Q. O

O

en

00 <D

"U

(0 .

^^

Q)

c

1

_

D

a

D

(O Q.

 I

1

00 Q.

o

O

o

)

U

O

o

CT>

in

(0

•H

in

o

)

T

S

3

1

4J

+J

(0

e

+J

•H

n

•H

^r X!

C

3

o

o

c

+J

•H

c

3

0)

•o

P

•rH

88
—, m co N 0) o —: o o o o T0^ m m in in in

O

o o o o o

m co N N OD

0_

_l

_

m

j

Q.

CO

O

co a

00 Q_

, O

\

J

 \

l ' -

\i

f -

J\

1

X

K

4

\

 :

1 ^

—

—

I l l I I

r00 (D

TJ

CO

^

 »

-t en

0

c

)

o

^

 c

CM Q_

li

1 -

D

M

CO Q_

00 Q.

o

o m o m o m o 1

CN T- t- o O 0) OJ

•r

o

H

r4

•H

ft

to

to

O

o

*

0

•O

)

0)

Cs

ft

JJ

3

ft

O

to

tr

I

4J

•H

>

a

•H

73

'

•

 p

EL

ro

u

o

c

-p

H

,

gp *|9A8| ajnsssjd punog

89
—i •<*• co m N oo

-i o o o o o

Z

O

 o o o o o

x^ m in 10 r-- oo

Q

m

_

_j

Q_

C/)

g

OQO O

v

*\'

rt

o m o in o in

CM r- T- O O 0)

t— T— 1— I— T—

gp *|aA9| ajnssajd punos

O

CO Q_

7.9- 5

O O

.— -H

7 ^ I o

J

(C

3

en

00 Q)

"O

(0 .

Q)

CM Q.

' I

IS

O

<? Q.

' I

00 Q.

O

0

o

)

&>

A

CO

4-1

a

0

•O

)

O

O

4->

•H

c

90
z

o

O »- *- CM O tO

o o n o to o

CM CM CM CM CM CM

o o io o m o

m CD co N 1-^ to

o<c

CM Q.

D *-

<? CL £

I i Q\

co a .

p

0)

•o

83 OD<><]

CD

_J

CM

o m Om

O

o

O)

in

gp '|8A8| ajnssajd punog

CT>

to a)

CD .

CM

O

CM Q.

CD n

' I

to Q.

o

p

o 1

0)

I

(0

•o

m

c

 3

D ^

0) 3

C

O

C

J

D

3

I

PM

•H

91
•<* m to

o o o

C

O

O

o o o

in co N

8j OnO

§

in

Q_

m

CM

o m

o

m

o

o

en

m

gp '|8A8| ajnssajd punog

I -+J

O

(O CL

00 Q.

01

00 Q)

(O

cn

c

CN

Q)

CM Q_

'

1

 1

 i

00 Q_

o 1

en

ft

V

(C

+J

•H

J

!

CQ

fO

x:

0)

•o

M-l

p

0

•o

fc

•H

O

O

4J

•H

92
O

•'t if) CD N

O O O O

10 co CD co

o o o o

m co r^ oo

Q

m

.

C

g

O ••4

11

o m o m o m CM «- • «- o o en

gp '|8Aa| sjnssajd punog

CMQ_

1

O

J

\ \

^^k^4 1

v^ 1

Y

^Vv

\

\

N

1 1 1 1 0

1

00

1

(O

^ ""

•*

»

> :

^^

^ A '

v 9

0

0

0

CO

CN

O

Q

1

.

t

O

-

i

0

M

~ch

0

o

c

)

o

c

•

ft

-rH

0

ft

.p

)

^CO

4J

CO

•r

1

B

H

0

ro

1

o

0

c

•H

3

0)

•o

)

•H

CN Q.

I -

O

M

CO Q_

00 Q.

O

0

o

1

93
Tf m (o r- oo

O O O O O

00 00 00 00 CO

Z

O

 o o o o o

\£ m u> N oo oo

g

co

Q.

m

C

O

M

*

\

I •

 V

/

 \

IT) 1

O

0

O

O

o>

m

gp '|9A9| ajnssajd punos

D

CD Q_

1

 I

00 Q.

t~

O

I

cn

CO Q)

(O

CM

0)

O

 c

_D

CM Q_

' I

JI

I

(D

O

00 Q.

O

cn

o

•H

4

to

.p

a

a)

J

(D -

T

3

(D

3

ro

I

U

O

4J

•H

94
C

O

O

tn CD N oo

o o o o

0) en o) o>

o o o o

in co r^ oo

OnO<]

DQ

0.

C

g

O

CN

•

in

O

m O

o

0)

gp '|OA8| ajnssajd punog

D

CD Q_

00 Q. Q,

' I ~"

 >r

1

00

10

(D

o

_

 C

D

CN Q.

O

® CL

00 Q.

o 1

0)

C

3

s

o

-

P

95
—. ' O CM tO 1^

-Jo e o o

Lt. ^ i- ^- ^

V)

Z

O

 o o o o

\y/ tn (0 I *

s

 ID

CM Q_

'

c

1

o

<N

o

00 Q. tr

I .— -

•H

a

H

o

h

8-

S §

s

CO

CL

m

••4

m

o

m

o

o

0)

m

O

o

)

gp '|9A9| 9jnssajd punos

en

03

(

CM

0

cn

_D

D

c

CN Q_

D

cp Q

' I

oo Q.

o

p

mi

00

m

3

4J

-P

to

•o

fi

•o

Q) ~

(0

P

M

*

O

4

•-I

U

$

Over

a

a

0)

fe

•H

3

M

96
— j o r- CM n

Z

o

 o o o o o

^ m CD r^ h> oo

OaO<l a

m

o 10 o m o

r- O O <J> 0)

I +->

O

CD Q_

00 Q.

o

p

• • n

^

 : ' f ' Hi i^

id

«

Mfl —

1

I

ffr

^^4

•

 ' —

—

I 1 ! 1 1

en

oo Q)

T)

CD .

O

rt cn

c

C M

0

0)

O

 C

_D

CM Q_

1 1

1

't JC

1 • '

1 "1" '

D

CD n

1

 1

00 Q.

^

O

-

00

•

O

o

m

(0

^

4

0

a

4J

•O

•H

1

B

•H

CO

.p

I

.p

•H

3

•O

0) I

(0

ft

 •«*

-P <

(1)

VJ

C

3

P

•^

fe

gp ' 9jnssajd

97
QzO. cnDO_l Q_O

S ^O^

~Z- 1 I 1

I ,1 1 -*-

1 D

<0 Q.

1

 |

00 Q.

| » —I

•!••

11 0

——

JU

JOOD

-^

"oO _

~^0"D

-_

\ \

cn

00 Q)

T>

(0 .

_Q) C

CM

 DQ) O

 C_D

CM Q.

1

 |

1 H1 D

00 Q.

o

D o m o m o in I

- f- O O O) 0) 00

gp '|aAa| ajnssajd punoc;

•^

•ro\

M-J

•rl«H

C/ wOor~J

ft 4(0

ft(U

•O+J•Hj•

ft*CO 4J(0

*"OX•Hi•H^\

a•a) 0i1oOC•H3)C3r •H

98
o

D

:

1

m

o

0

Clg

lO

•* ID m h- oo

o o o o o

r» r^ i^ r- r*

o o o o o

in m <o h- oo

OQO<I

m

O

m

O

o

0

m

) 0

o

)

CM Q.

' I

•* -C

i -

D

M

co a

' I

00 Q.

en

00 Q)

T)

(0 .

_D

CM Q.

' I

* -C

I -4-

1

D

CO Q.

1

 I

00 Q_

o^

in 1

00

V

(C

ft

&

4

0)

4-

s

•H

)

C 2

(D

3

a)

•o

D

S

k

0)

u

O

C

-P

•H

I

fa

•H

gp '|9A8| ajnssajd punos

99
— ,

z

o

-

o i- <- CM o to

o o n o ro o

CM CM CM CM CM CM

o o in o in o

m CD <o r- r- oo

OaO<]

CO

CL

m

m o

o o

m

O

o

)

CM Q.

I I

<0

O 5

00 Q.

o

p

^

I

cn

00 Q)

T)

(0 .

O

°l

CM Q.

* x:

i -*-

D

>

(O a

' I

00 Q.

ml

00

4

CN

o

J

>-

•a

i

B

•^

co

4-1

•a

«

D

3

VJ

(I)

cS

4J

•H

3

<D

•a

I

•H

gp 'pA9| ajnssajd

100
-D. 0O10 00

n n n o o o m <D h

CO

o_mjg

•4

«nO

Oo0in)0o)

Q. I °°to

 a .

ft I ;— +Vl

ITSJ•a0)

TO4J(0•s

00 Q) (0 •° I c, 00c) CM Q. ' aD oo CL I •"""

m 1 00

14-1

t0l) 0«§•HC) C3hP

fc•H

gp '

101
a

D

z

:

co ro o

(0 CO

Z o

o

o

v r^ oo

D

I

O

On

"

in

o

in

o

o

0) 0

o

)

' I

•* s

O

i

10

CO Q_

cn

CO Q)

TJ

co .

CM

_O

(D

D

c

CM Q.

CD Q.

' I

00 Q.

O

ml

00

a.

0

(D

ft

.p

+J

•H

)

4J

C

&

O

i

0

•O

)

0

C§

-P

•rH

C

)

V

p

4

tr

gp '|aA8| Qjnssajd punog

102
O

-4- m <o i^ oo

o o o o o

oo oo co co co

o o o o o

to oo oo

§

CO

Q_

m

•••44

' I

* -C

I -

D

V

<D o

' I

00 Q.

00

O

 Q)

(0 ,

<D

c,

O

0

C

CM Q.

' I

I -

D

H

« a

1

 I

00 Q.

ft

0

•O

4J

•H

)

(-1

(0

4J

4

W

J

1

•H

S

(D

-o

•rH

4->

<

8

C

u

t-l

3

o

m

o

o m

e

o

n

ml

00

gp '|8Aa| ajnssajd punog

103
— . m to i^ oo

- o o o o

ft. en o>

Z

O

 o o o o

m co h- oo

Q.

_

m

i

CL

O

o

in

o

o

c»

m

0

o

)

IN Q.

' I

I -*-

D

>

«> Q.

' I

<D Q.

oo

O

 0)

T)

(0 .

Q)

O

 C

CM"Q.

I -

D

^

(0 Q,

' I

00 Q.

I |

ml

(O

C

4J

(0

ff

s

4J

•H

O

t

0)

!

C

3

a

8

C

O

rH

P

•H

gp '|8A8| ajnsssjd punog

104
D

O M CO N

O O O O

Zo o o o o

^ in <o N oo

OaOO

CD_i a. in

m o o o in o o> en

' I

(0 f)

1

1

eo Q. 9oI- 01 (D Q) TJ (0 .0) CM Q. '<o n ' I CO Q. I :— ml co

CM

M- •Hi -P•Hagh- twist standar

VO4J•H) b. (0

 C°

I O M

 C

Q> * 3 § I*ao•oII

 "

gp '|9A3| ajnssajd punos

a•o1 4J

r-•Hs•H\ICO •a.Q(0•Oera 03a> •H

0

iHOO•HZ)05U

105
is;

V)

Z

O

 o o o o o

in <o h- h« oo

7f

tO O

' I

00 Q.

I I 1 I 1 1

1

o

OnO<

CD

Q_

CO

00 Q)

•D

(0 .

Q)

O C

7

D

f

03 a

1

 I

oo a

in

o

in

o

o

o>

in

a

o

t

in I

oo

0

•o

ft

w

o

o

CTi

in

(0

•H

O

•H

)

Cs

ft

O

+J

to

C

i

+J

•H

n

S

D -

u

o

c

-p

•H

c

0)

•o

fa

•H

gp '|8A8| ajnssajd punog

106
1 ^ ~~

? in w N o> o OQ — -J o o o o iQ£ in in in in tn

f/l

1— ^ —

Z

o

 <3 Q p p g j

' O

1 •*-• £

O m

f Q- ^

1 <

oo o i

!.— <->

H w -o o c2 <u

«- 9

1 o, .S

'13 ^

> '

0) °

 S

^" -1

a! i/ w 0 nO<] ^ • -

CD 4l

^ ^ 1

X

. //\ ^^ • ^^ ^ij ^ ^^ H _^__

v// VV •§ ^^ ^^ • "v ^^

O 1 A _

\ ^

/

• —

—

2 « '.

Q) jj <<

« 0) ^ a)

T3 ft £

(D •> •* -H

0)

 M

 fc

~~ •

p

c »

N D Y

Q) Oi

JO. ^

1 1 '

D

<o o

00 Q.

1 p

O

in o m o in o in 1

r- i- O O 0) 0) 00

gp '|8A8| ajnssajd punos

107
D

-«J- <o m N «o

_- O O O O O

Ze o o o o o

«n m <o r-- w

OaO<]

CD

_i

CLg

IO

'f

T

O

• * "1

\

t

tf

T

• \ _

1 1 1 1 1 1

0

o

) Q)

TJ

<o

_

 .

Q)

5

O

 C

CM^.

1 ^

D <0 Q_

' |

« Q.

^^

in o m o m o inl

T- i- O O 0) 0> tO

5

Ou

(0

(-1

cC

•H

O

-P

•H

a

— -o

c

•o

&

3

H

0)

O

4-1

-H

i

fa

•H

gp '|OA8| ajnssajd punos

108
-•j O r- CN

Ct CM CM CM

2

g

 o o o

v in <o S

_

m

j

Q.

01

§

OnO

•4

o ~

CO

T

(D

 Q_

ID

oo

T

O

0)

IIT-^

CO Q.

I :-

IO

o

in

o

o

0)

m

o

o

>

ml

oo

tr.

s

a

CO

4J1

(C

•o

•H

c

0)

•o

I

o

o

c

•H

•

o

in

3

>

•H

gp '|8A8| ajnssajd punos

109
in

to

cn

Z o o o

> in <o hCD

CL

CO

in

O

m

O

o

0>

m

0>

o

'"5 <0 Q_

' I

eo Q.

I :~

oo 0)

T)

(D

0)

(U

7?

(D Q_ 1

 I

«0 Q.

ml

00

>J

(0

T3

(1)

<C

^->

CO

4-1

I

-P

•H

T)

<

g

U

<

in

U

O

4J

•H

gp '|9Aa| ajnssajd punog

110
•* i

n (0 r^

o o o o to to (o to

Z o e o o o v m <o [^ t) Q. OQ_ _Jm

C

IOoo Q

)

TJ

(0 M CN 0a) I fD 7f op CL I :—

IB•Hto-p0)cu+J-H&

30) •oUO+J •H in Oin Oo 0in) <Jo> in 1 00 gp '|9A8| punos
—> •* in (o IN oo

r^ O O O O O

fr 00 00 00 00 00

Z

o

 o o o o o

v in <o N oo oo

OnO<

CD

_j

Q.

O

in

\ \

\

 X

 \

*>^

o

in

1

o

o in

0

o

)

gp '|8Aa| sjnssajd punos

« a

8

•a

,

4J

03

«o 0)

c

n

n

c

0

rt

o

o

c

+J

•H

g

0)

•o

)

C

3

M

n

•rH

"5<D Q_ 1

 I

?,s8'

112
- *_

-.

z m <o h- oo —

^222 2 If VI O) Ol Ol

H —

-

0

 S § P § ' ' ' '

CM"Q.

•* J:

i • *

' 0

<o a

00 Q. i

1 *— -

1

-

1

o

•*• i « . • 3

> r p

4J

M

j M -i

§OaO<1 4«*

m y\ v _

Q. A /\ \ \

oo • • • ^ -4 -4 • A — <

 w

 ^^ \ \

B

 TM o \ \ \ \

\\\

—

—

—

1 1 1

O co

r- *rj

CJi *>

00 0) s

"O S

<0 * —

J) ^

^ Q)

C

CM"Q.

T

D

£

(D f)

00 Q.

O

m o m o in o ml

«- r- O O 0> 01 00

•

CD

•c

i-l

tl

3

CD

1

u

0

U

gp ' 9jnssajd

113
O

f

O <N ID N

O O O O

COh- 2o

 o o o o

v in «o N oo

aoIa

03 Q_

V

c c 0 O

•H JS

4-1 04 o o C M s o

-M.H

Sfi 0) O

OnO<I

CL

(/gO •••

4

omoo

0m)0o)

oom

n•d

°

.0

 I1 5

oo o M T> +0}J

ID . -rj

_Q) 5

*? s

N° : (U 5 D

<? a 1

 I

op a ' io i 00

o

(1) CO

Vl 3 O to +J

S * to

4

m

 8. T) 0 C -H _g g! TJ W c $ a > <VDor

gp '|3A8| ajnssajd punos

114
O r- CN

C

o

O

Z o o o o o

\/ 10 CD r^ f^ oo

c/j

m

o

m

o

o

0)

m

o>

o

00

m

CM Q. X

O

co Q.

1

 I

00 Q_

Ol

00

14-

0

•H

1

n

•H

)

C

T—

o

CT>

m

J

0

<D

•O

W

a

)

<0

to

+J

a

-p

3

•H

en

oo Q)

T)

CO .

M-~ai

_

(D

c

 ja

CM Q. ^

I i

O

CO Q.

00 Q.

0

•O

)

3

C

3

V0

O

O

4J

•H

P

gp

 4

|aA8| ajnssajd punos

115
C

z

o

co

on

D

L

C

m

O

_j

0.

C

g

O

•

o

0

I

^

CM Q. -^

1 •-!

•H

D '

O

5

oo n i

1 .- u

o

1

" 5 *S

t C

_j *H

I>

 4J

* <§ 0) ^

•~

—

—

0)

-Q —

'5 —

D

D

 ~

-i—i

•o

O

 —

o

s

 1 ^ cn ^ <

00

 d) Q)

~n ^"^ LJ V^ Qj "

— -P

•^ ^) (0

CN§ |

Q) cn

°o :

7a »

•*x:

i •*->

o

co n

' 1

to Q.

1 •—

>

3 m o m o m o 1

O O O) 05 00 00

gp ' punos

116
—. •* ID m I

s

- oo

r-J o o o o o

[£ I

s

- I

s

- I

s

- r* I

s

-

C

O

O

~Z. o o o o o

v m in co I

s

- oo

OnO<l a

§

in

CL

m

CM "Q.

1

 I

* JZ

I •*-

D

>

CO Q_

•* -

'A —

J | V

444 —

J ^\ _

\ . »

-

4t^

\ 1 1 >

L

TT"^

^1

^^ 1

\

^

 -

—

1 1

v^

en

00 0)

TJ

co .

Tf "en

c

CS°

0)

o

 c

D

CM Q,

1 |

1

1 -*-

D

>

co a

' 1

00 Q.

O

o m o in o m o 1

i- O O 01 0) 00 00

^

£

h

<o

a

o

j

CO

B

•H

VO

u

o

c

.p

•H§

(V

•a

gp *|aA8| ajnssajd punog

117
o T- ,- CM o n

o o K) o n o

CM CM CM CM CN CM

~Z

o

_ o o m o m o

v m to to N i^- oo

Q_

(/)

_

m

i

Q.

O

!S

< 1

o

m

o

o

cn

m

o>

o

oo

m

gp '|aA3| ajnssajd

g

CM Q.

1

 I

-t1 43

g. 5

00 Q.

cn

oo G)

TJ

CM

to

_0)

Cn

C

D

C

D

CM Q.

D

tO Q_

 I

1

00 Q.

\F

o 1

oo

10

*

10

+J

I

C

-P

•H

O

3

^1

ID

U

O

4J

•H

I

•O

i

•H

118
't in 10

o o o

h-

^

o

. o o o

•y lO (D N

CS Q.

' I

<*• JZ

"o

CD n

_

m

J

a.

s

to

OaO

1 1 I 1 1

oo n

i • —

I

i—

>

• ^b °

n ^^^

/ / \

it A —

A • \ - —

rCP

to 0)

TJ

to

i t

•H

Aanhedral 1

D

-P

)

.,-

IS

1

4

I

1

J

Continue

d

i^

<

^

3

M

U

tn

.r4

^ fe

<4-l

(D

°5

IN a

o

(0 a

1

 I

00 O

o

O

O 10

O) O

o

l 00

in ol

00

gp '|8A8| ajnssajd punos

119
D

to p^

~ ° ° C£ to to

C

Z o

O

O

o

•y h> 00

Q.

DQ

_l

Q.

On

o

m

o

o

0)

in

o>

o

oo

m

gp '|aA8| ajnssajd punos

CM Q.

' I

^ SL

I -

O

M

CD Q_

00 Q.

00 Q)

(

CM

0

(D

CM Q.

' I

•* ^

I

O

*

f

00 Q.

O

01

00

4

a

J

<D

0

.p

}

I

-P

•H

-

0

0

I

)

4

o

c

J

o

120
\A ~

5 -d- m co t^ co X — — > c? o o o o M

(Y. 00 00 00 CO 00

h- —

Z

o

 0 o o o o | i | |

•y U) CO I

s

* 00 00

CM Q.

T

D

£

CO Q^

CO Q_

1 J "^

O

1

M

^> •

^_^ O

Q_ l\|

(/) (y n \/ ^l (\ ^k^^k —

m ^\ \ _

i ^ ^| ^p

°- ^.^^ ^

 !

 \\ \

^0m+4 A 4 4lt

o \V\

^^

^M ~

T" _

V

\

 _

^ —

I I I I

rcn

oo (D

T)

CO

Q)

C

—

CM

Q)

O

 C

CM "Q.

1

 1

* J

O

I

CO Q_

' |

00 Q_

l^

o m o m o m o 1

T- O O tjk Oi 00 00

c.

•rH

4J

Tl

fO

ft

0)

ID

*

J

1 i

CO

•r

£

^-~

a

i

B

H

i

CJ

0

c

jj1

•o

*

Pu

•H

(D

IS

gp ' ejnss9jd

121
m to r- oo

o o o o

o> o> en o>

Z

O

 o o o o

v in CD r^ oo

Q_

CO

_l

DQ

_J

Q.

O

«

0

m

O

o

0

m

) 0)

o

CO

m

CN Q.

D

CO Q_

00 Q.

T

O

en

00 Q)

T>

co .

<D

°l

CM Q_

co

00 Q.

o 1

00

B

•H

CO

•P

3

<B

a

v<

a>

rt

VD

u

o

C

O

iH

•s

a)

-o

I B^ -H

gp

 f

jaA8| ajnssajd punog

122
-j O CM CD

o:

O O O O

h-

"Z

o

. o o o o

\£ in CD t^ co

OnO<!

CD

_l

Q.

O

1

 I

7£ ~

D *

CO Q_

00 Q.

I |

1 9^

<\

•^9 ^

4v

^

'

1

C

1

O

0

1

0

H-J

Q

D

_

a

1

D m o m o m o 1

- o o o en oo oo

CN Q.

'

CO

CM

(D --Z

u

c S

0 0

'•p ft

CJ O

C M

3 O

CO

m

 0

n) <4H

CO OJ

o

o

7

o

o

CD

Tt

CD

TJ

_0)

n

C

*

a

^

-P

•Hstandar

d

4J

CO

C

i

3

-H

n

X

•H

0)

(V

>soun

d[ pressur

e

•

0

0

)

-p

(=

•H

C

O

5

^

3

O

Lf

0

>

>

s

M

(0

c

w

.

•H -M

i-H -H

I O

•O O

C rH

5 2

•s s (C >

o

gp 'pAai ajnssajd punos

0)

a

&

)

fa

•rH

3

123
D

o i- CM n

Z

O

 o o o o o

v m (D I *

s

 I

s

- oo

Q.

00

OnO<

o

m

o

o

O

m

) O

o

) 00

m

' I

-* JI

I -f

D

J

(D o

1

 I

00 Q_

T

O

cn

co Q)

"D

(0 .

0

c

)

o

_

 C

g

CM Q_

D

.a

00 Q.

0

o

3

MOJ

U1

T

ft

o

)

0)

0)

0

ft

JJ

(C

ft

I

2

5e

s

+J

•H

D

(V

•O

.

0)

&

3

M

>

fe

•H

gp '|8Aa| ajnssajd punog

124
O O O O

m in in in

Z

O

H

 o o o o o

v m to s I *

s

 oo

Q_

_mJ

_i

Q.

O

o

m

o

o

en

m

en

o

oo

m

gp '|8A9| ajnssajd punog

D

to a

' I

oo n

oo

en

(0

CP

0

C

)

_

a

o

tO Q_

' I

00 Q.

O

o

O

o

14-

O

•H

1

i

CO

4J

0)

ft

41

&

.p

-H

w

w

O

"^ u

tJ

p

8

0)

•o

l

fa

•H

125
—, •* co in I

s

- oo

r^ o o o o o

G

O

O

Z o o o o o

\£ m m co N oo

Q

m

1

.

OnO<

1

o

0

o

o

a>

in

a>

o

oo

m

CM Q_

I i

D

CO Q_

 I

1

00 Q.

oo 0)

T3

CO .

CM

<D

D

C

CM Q.

' I

00 Q.

o I

oo

C

•P

•H

J

o

1

&

id

J3

O

•H

^

ac

•H

3

<D

•o

c

<C

r8

C

4J

-H

r

PM

•H

gp '|9A8| ajnssajd punog

126
o i- «- N o to

o o n o n o

CM CN CM N CM N

Z

O

 o o m o m o i

\^m<o<oi^r-o o "-

•k

DO

OnO<!

D ~

Q. .o

00 Q.

00 0)

(0

Q)

o C

D <o a

00 Q.

O

ro

C

tt

M

0

-P

«

TJ

(d

•s

•P

•H

)

0)

I

•H

0

•O

)

ft

rI

4->

•H

C

s

O

m

O

o

O

m

) O

o

> CO

m o 1

00

gp puno$

127
-d- in <o

o o o

to 10 n

Z

o

 o o o

v in CD N

CM Q.

1

 I

I -

0

^

to a

' I

CO Q.

D,

•rt

id

o

O

C

4J

•O

D.

(f)

DO

_J

Q_

O

•4

O

in

O

o

0

m

) 0

o

) 00

m

gp '|8A8| ajnssajd punog

00 Q)

T>

co .

Q)

Q)

_

a

D

I •*-

D

>

TCO Q.

I j""*

o 1

00

(0

•rl

>t-i

r

e

CM

•H

128
O

•* IO <0 1^

O O O O (D CD (0 (D o o o o in <o N oo

ODO<! _mj a. co

<N Q_ D « a 1

 i

00 Q.

O

cn

oo Q)

T)

(O . M DIa(DDC (O Q. ' I 00 Q_ O

oto

oo

0)oo

in

ooo

ft

••HJJ

4-1

ft

.9)

4Jcn s4^-H

0•D) uoC

gp

129
•* m to N co

o o o o o

co co co co oo

Z

o

 o o o o o

v in CD I

s

- oo oo

Q

m

1

.

OnO<] a

o

m

o

o

o>

in

0>

o

co

m

gp '|aA8| ajnssajd punog

CM Q.

' I

D

CO Q_

00 Q.

o

F

 *

I

co

01

TJ

c

(O

,

D

CD

00 Q.

o

o 1

oo

I

Z

•H

CO

a

0)

a

0) ^

0

D

)

Q^.

0

•o

)

0

o

o

c

+J

•H

3

M

)

C

3

n

b

•H

130
O in t

o ^ co

O O O O en o> en o> o o o o in <o N co

OnO<]

_mj Q. COO

CM Q_ D

cp Q.

CO Q_ oepn 00 0) T) to .0) CM Q- D CD Q_ oo a. o

OinOo01m

0o)

00m

o 1 00

a

:

3-H(0COV3•H

fa•Huoco

iis•a0) •o

gp *|9A9| puno

g

131
O CM CO N

O O O O

C/)

Z

O

O O O O

in CD N oo

CM Q.

co Q_

00 Q.

O §

?!

S *

<2.^

«

 e

Vl

CO O

<0 4-1

M CO

>H .p

Q) O

> C

CD ^

, o

_

m

j

CL

(/

g

)

•f\ "I

r > ^ tAP ~~

' \ \ /

1 i ^J|L

^•j^^

A4

—

I I 1 I I I

oo

'-

 0)

CD «

_0)

rh cn

0

c

)

o

 c

D

CN Q.

| .

1

^ JZ

1 -

D

^

CD Q_

 1

1

00 Q.

o

>fZ

m o m o m o in 1

r- T- O O 0> 05 00

•astandar

+j

CO

K

•rH

i

B

•H

UI OU

3 0

CO -P

CO

CO 0

(-1 ID

ft

•d o

D «4-l

co

0

 a)

tr<

-o c

a) «

-p M

E

•H

 >,

m I

gp *|8A9| djnssdjd punos

bandl

velocit

an

d

over

Over

a

C

D

o

O

•H

132
o:

o

o o o o o

m (o t^ t^ to

CM Q.

' I

D

00 Q. °

-P

•H

a

4-J

O

•H

8

-P

•H

3

CD

•O

&> OnO<

m

m

o

lO

o

o m

O

o

)

gp *|aAa| ajnssajd punos

o>

00

T

 0

J

(0 „

Q)

M

Q

D

c

)

CO

m

4

s

a

J

CO

4J

CO

a

•H

_ J3

CM Q. "-

o

CO Q_

I i

00 Q.

O

fa

•H

s

133
O

in 10 h- o> o

o o o o *-

in in in in in

o o o o o

. in to r^ I

s

- co

O n

~O- .7

a

D

<n a

ft

•a

QnO<l

o

<

CO

CL

m

in

o

in

o

o

0) en

o

gp *|8Aa| ajnssajd punog

(0

<D

o

•8

f g,

» £

Q) "S

O

 C

 ^.

_D 3

CM Q.

D

» a 1

 I

CO Q_

O

ml

00

134
—» ^ CD If) N 00

•r: o o o o o

Z

o

 o o o o o

^ in m co r^ 00

CM Q.

' I

*.H

I ->-

D

>

CO Q_

' I

00 D.

' F

X

•H

O

4J

•H

!

(C

(1)

8

3

_J

D.

_

m

i

CL

O

3

OnO<] ^

in

O

m

O

o

O

m

) 0

o

)

gp '|aA9| ajnssajd punog

oo <u

TJ

co .

CM

ml

00

4->

CO

C

•H

P

-O

DC

•H

c'

Q

D

)

D

C

CM CL

' I

O

CO Q_

1

 I

00 Q.

IF

C

3

a

P

•H

135
O

O i- i- CM O K)

o o to o ro o

CM CM CM CM CM CM

o o m o m o

in to to r^ N oo

&J OnO<]

m

10

o

m

o

o

o>

m

en

o

CM Q.

(0

D ~

CO Q.

a

h

•O

)

TJ

(0

+J

e

O

n

(D <u

C7i

00 (D

TJ

co .

°5

CM Q_

D

® Q.

' I

CO Q.

ml

00

0)

0

u

O

^J

•rH

C

3

)

V4

PL

•H

3

,

.

gp '\QAQ\ ajnssajd punos

136
•«• m <o

o o o

n n ro

Z o o o

\s \n 10 t>>

OnO

DQ

_l

a.

O

in

O

m

O

o

O>

m

O

o

)

CM"Q.

D

O Q.

' I

00 Q.

10

(N

_Q)

Q

C

)

CM Q.

O

(0 o

 I

1

00 Q.

O

ml

00

V4

T

m

C

3

a

8

)

fo

&

^

gp '|aA9| sjnssajd punos

137
O

^ IO ID N

O O O O

(0 (£> (0 (O

O O O O

in CD i^ no

DO

a.

C

g

O

o

m

o

o

05

in

O

o

)

gp '|9A8| ajnssajd punog

<N

D

oo Q.

_ 4-

ft

J

4J

CO

•H

01

CO Q)

TJ

(D „

(D

C

O

 C

CN "Q.

D

CO Q_

1

 I

00 Q_

O

00

m

^

0

•O

)

4-

•H

3

O

>

ft

00

U

.

•H

&

138
(f)

Z

O

*• in <o h- oo

o o o o o

00 CO CO 00 CO

o o o o o

in CD r^ co oo

CM Q_

' I

D

to Q_

\ i •

I ft

00 Q. -H

o'

H

 -g

" ft

(0

4-)

0

•O

)

cS

3

OnO<l

CD

_j

Q.

CO

m

O

m

O

o

0>

m

0

o

)

gp '|9Aa| ajnssajd punog

cn

CO Q)

T)

CO .

C

°

M

l

CM Q.

' I

I ->-

O

>

10 Q_

00 Q.

O

ml

00

cn

i

4J

-H

C

s

P

fe

•H

139
—, in to r^ oo

-i o o o o

UL 01 0) Cn 0)

C

o

O

Z o o o o

V IO CD N 00

—

i i i i i

1 I

1

^ JI

l • j

1 -i—"

D

CD a

1

 1

00 Q.

o

p

 3 i r- 9)

co

CL

0

g

0

fvV 1

•^ • Y \ ^

<v. ; \ \ \ TM

^ A

X

 V

\ ^ *

•M:«

•4^ • ~ ^ v •

—

—

—

1 1 1 1 1 1

o

cn

00 Q)

T3

CO .

Q)

_i. rr> ~ \s '

C

^, ° CM

Q)

o c

D

CN Q.

' 1

^ _C

1 • '

1 "*-"

0

 '

CO Q_

1 11

00 Q_

o

p

n o m o in o ml

t- O O 0) 05 00

3 §

8" 1

3 ' B a

4 at

1 s M

 Cn

_ -H

5

 fo

gp '|8A8| Qjnssojd punos

140
O C

M <D

Zo o o o o

\x m <o N oo

.j/j m

o m CM T- 8P

o m o m i- O O O)

sjnssajd punos

1

 ID (

0

0- «

I CM

00 Q.

cn

00 0)

(0CMCM

JcDnQDc) a

1

 I

*.ni -t-D>

(O Q

 I 1 oo i

 a0101

r 

§ §

^ c

to

rH i)

ftVT) 4J•HJ<•g«c

4->

CO

+J(0OI+J•Hi ^^s

 -ins

§

3.8

e >,

4J

7

 -H

i*

JS a; CM

 ^

0o5M1CrH)Vl O3i

•rH

141
01 •* •* •* Tf

C

O

O

Z o o o o o

\£ m CD r- N oo

CM Q_

I i

D

CO Q_

' I

CO Q.

o^

CT

m

m

•H

O

•H

i

e

o

o

n

D

•o

+J

-H

o

O

-P

•H

s

t)

•a

._]

Q

m

_ OaO<

C

O

M

m

o

in

o

o

cn

m

cn

oo (D

CD „

rj-lj)

(D

c

O

^

 C

CM a

o

CD Q_

00 Q_

0

P

O I

0)

+J

0

ft

)

4J

CO

3

•&

Oi

&

P

i

gp '|8A8| ajnssajd punos

142
m (

O N

O O O m m m

ZO O O O

DQ

Q_

0S0

I -DM

(O Q.

1

 I

00 Q.

en

00 Q) T> (O „

^"o>

<cDDcu

(O o

 I 1 CO Q

.

•rl CsOJ T

ft wwl 0)CO

ft

ft(D

iB•H

V(D

CTi uoC4J•Hgi O3i

fc•H

CMO

m

om

oo

o>m

0o)

gp ' ajnsssj

d punos

143
•* CD m N oo

o o o o o

Z

O

 o o o o o

\^ m m CD h- oo

8

_

3 OaO<l

DQ

\\ I

/Vl — LK

\

1

>\

\£r

i\

M3

—

1 1 1 1 1

CN a

1

 1

-* .c 1 t 1 1 -*— '

D 10

 a 1

 i

| Q^

<o a ^

r~ o

1 o

Q

rrt

m

i

A O .u

| ^T

' \

•^ — i

\

J

A^

J

\n ~

^

i

» i

4

 :

1

i

,

 _

^

1 1 1 1 1

•" to

D) -g

00 0) +>

"D J3

10

 • a3

-5 ^

C "

(D

o

 c

D

<N a

1

 1

•* ji

i -*--

D

CO Q_

' 1

00 Q_

f^-

0

•O

)

fc

•H

3

ID

*

1

CJ

o

C

•H

p

D m o m o m o I

N| T- T- O O CO 0)

gp ' puno$

144
O i- i- CM O P)

o o n o to o

CN CM <N CM CM CM

CO

Z

O

 o o in o m o

\ m ID <o r^- i^ oo

DQ

_J

Q

1

_

OnO<l

CM Q_

' I

-* J

c

o

Z

n

oo (D

T>

10

Q)

0

°°

CM Q_

I I

I -+-•

O

(D Q_

1

 I

00 Q.

m

V

1)

CJ

O

4J

•H

3

0)

•o

I

tP

•H

CM

O

o

m

o

o

0

m

) 0

o

1

gp *|9Aa| ajnssajd punog

145
•* m CD

O O O

ro n to

(f)

Z

O

 o o o

\s m CD r^

CD

CN

O

o

o

O)

in

CL

CD

O

1 1 1 1 1 1

C

o

1

O

T—

Q.

hanhedral ti

p

cn

oo (D

_Q)

cn

(U

c

O

 c

CM "Q.

^ J

D

I

10

 Q.

oo Q.

o

0)

a

|

5

g

gp '|8A9| ajnssajd punos

146
C

o

O

2

-^ m CD N

O O O O

ID (D (D (D

O O O O

in (D N oo

a.

C

s

O

CM Q_

' I

T

D

£

CO Q_

' I

00 Q_

01

a

a

3

•o

** —1° •r 9

/[ \

• •v ^^ ft ~ F

' \ \

\\"A :

\ \ *\ ^\

\ ^ • • ~~

\ \ \ \

\ \ \ \

<*••

—

1 1 1 1 1

i —

cn

oo Q)

~°

(0 .

(U

c

O

 C

CM "5.

t 1

1

•* JC

1 -4-

o

-

CO Q^

00 O

5 C

CO O

u

4-1

CO 1

•rH •

> cn

•P <

S CD

S 3

tn

--» -rH

D in o in o in o 1

M r- r- O O , O) 0)

gp puno$

147
•* m co N oo

O O O O O

00 00 00 00 00

Z

O

 o o p o o

\ in CD N oo oo

c/j

s

m

CM~Q_

D

CD Q_

00 Q.

°

F

T

C

(D

ft

U

*,< H / /A

<V.\

/ \ \ \

\ *\*\

\ \ \

' +S*

\ \ -

\\9

—

1 1

o

rn

00 Q)

T)

CO „

rh"cn

C

^ <D

o ^

D

CM Q.

^ 1

D

CD Q_

1 11

00 Q.

1 • -

O

D m o m o m o 1 M «- «- o o en en

+j

01

s

a

I

4J

•H

(I

•C

I

4-

-H

g

>

u

§

gp '|8A9| ojnssajd puno^

148
m t

o N to

O O O O 0) 0) O5 0)

Zo o o o o

\£ m co r^ oo

*.

j}

CM Q. I

 I 1

 +-•o

CO Q_ 1

 I

00 Q_ .— -

H

o

3(0

u§u•oCD •o

OaO<I

v\ ~

CDa. C§O

\. \

CMOomooOm)

00 Q) 0(O, 0Dc) CM Q_ ' I ^ JDC CO Q_ ' I 00 Q_ O

(7o)

CD

•H

0) XJ

fo•Hd3

gp ' puno

$

149
O CN (O N

O O O O

Z

O

 o o o o

v m <o I

s

- oo

CO

Q_

m

w

m

o

m

o

o

0

m

) 0

o

)

a

co

00 O

I ;

en

-

oo d)

TJ

co .

CN Q.

' I

I -

D

M

to a

1

 I

00 Q_

IP

10 I

00

C 0)

o c

•H O

. o "g,

*~

x

 c o

(0 <4-l O

VD

C

tr>

M

•rH

M

ft

H

ft

M

•O

•P

•H

i

i

!

to

+J

I

•O

(D ^

o

•p

to

e

•H

CO O

V4 00

10 0

tO 4->

CO

id °

ft in

•O E

c p

3 (-1

0 1-<

to

CO

•O &i

CO C

4J (0

•H Vj

•H

E

 >,

rH -P

1 -H

•O O

C O

(C rH

.a co

(0

•o

 CO

rH O

(0

gp '|8A8| ajnssajd punos

0)

•rH

3

150
—j O t- (SI to

—* T- r- r- rCC •«• t •* "fr

(f)

Z

o

 o o o o o

\£ in CD j^ I *

s

 eo

>

7?- H

' I -g ^* ^ 11 [

'? -s CO o

' i

I o

 a

°?.9- 5

ft

<D

•o

•P

•H

u

O

C

4J

•^

C

3

OnO<l

_

m

j

Q_

5

to

o

m

o

o

0)

in

0

o

)

gp '|8A8| ajnssajd punos

oo <u

T)

(O .,

0)

CM Q.

' I

-* -C

I +-

D

>

co a

' I

00 Q.

ml

oo

0)

(0

•P

to

>

•H&

151
C^

Ha

m

O

.

c

g

o

\\

A

m CD I-** o> o QD — 0 O O O iin in in in in

o o o o o i i i

id m i*- i*~ in '

in \o p* r** ou

CMQ_

1

 |

1 -

D

M

CO Q_

' 1

00 Q.

I • — •

!,_,

^

i

-

* * n

2

OnO<3^ ("4

1 1 / ^^^^L ^•^ — // /

w 1 4 ^ 4 ^ 4 — ll 1

^4

\ \ \

J^^

^

\

 —

«

\

^ —

1

CP

00 0)

T)

CO .

<U

^ c

c •

n

CN ^

0)

° n

<N "Q.

}

1

 \

 -

D

M

CO Q_

1

 1

oo n

1 p

m o in o in o ml

r- T- O O 0) 0) CO

^^

•H

rHairf

o

0

O

i

0

w

to

.

0

•o

JJ

•H

)

cu

0)

"o

ac

••H

£

1

'S

CO

4J

CO

<D

"^

.p

•

0

'O

)

C

o

C

+J

•H

£

3

1.

J

^(J

2

5

0

l

CM

•H

gp '|aAa| ajnssajd punos

152
D ^ (D in h> oo

-, o o o o o

Z

o

 o o o o o

^ in m (o i^ oo

OnO<I

g

o.

m

m

O

m

O

o

<J

m

> 0

o

>

CM D.

I

'.c

i

00 Q_

co (D

TJ

(0 .

Q)

CM Q.

' I

•* JC

I •*->

D

« a

1

 I

00 Q.

m 1

00

•c

W

•H

B

•H

ca

<a

JQ

O

0)

I

o

O

C

C

3

*

o

gp '|8Aa| ajnssajd punog

153
D

O T- i- CM O rO

... o o n o 10 o

DC CM CM CM CM CM CM

o

o o in o in o i

m CD CD r^ N oo

 L

OnO<]

m-

_l

CL

o

0

10

O

m

O

o

0

m

) 0

o

)

I -*-

I

• D

CD Q_

1

 I

00 Q_

D1

CD Q)

T)

co .

CM Q_

' I

t JC

I -

D

M

<o a

' I

00 Q_

ml

00

CM

•rH

14-1

ft

0

•H

CO

•O

(0

h

•O

•H

)

Q) ~

T3

0)

3

0)

<

O

•

I

U

O

-P

•H

C

•H

gp '|aA8| ajnssajd punog

154
•* in ®

o o o

n n n

V)

Z

O

 o o o

m to t^

D

.a

00 Q.

O

T)

0)

0

-O

g

)

o

o

•H

OnO

CD

_l

Q.

10

m to

O O

o

0>

m

CO

o

gp '|8Aa| ajnssajd puno^

00

T>

(0

<D

CM Q.

I -

D

^

• a

00 Q_

o

to I

tO

+

CO

J

-rH

+J

M-l

C

3

n

CM

•H

155
•

* m to r^

o o o o to co (o to

Z o o o o m <o h- co CDQ. 0g0

•*<

\in om

oo

Oin)

0o)

gp '|aA8| ajnssajd punos

CN Q.

' I

•+JE

I -D^

<0 Q.

1

 I

00 CL

o

I

r-Oo^ D

Ic

CN°0)

°o

CM Q.

' I

't JI

I -D^

(D a I i in i 00

ft(0

4-1ID

ft

4->

4J

-H

•rH

cn 3

0) '

T) §

T30) 3M<0<O•IOO4J•H3

156
CZOL

(/) OsQ

1 J 1 1 1 VO 0 IO r- r- O

o

~Z- —— 1 1

^ ' 1 -DM (D Q_ 1

 1

00 Q.

1 j~

_. i o1t—

,

J5U

 ~" 'o _ oo

 —

"

0o^y 1 1

*-

CP

00 0)

TJ

(0

^

 .0DC)

o

_

 C" N Q

.

' 1 t _c 1 -D^ (o r\ 1

 1

00 Q.

o in o vnl O <J> 0) 00

cx

(1•o•H)

(11)

•H(0

.p

 -..

2Sf

0•o) 0<o1oocJJ•H3)CoP s

gp '|8AS| ajnssajd punog

157
oDZ: CL_JCO_JCLo

o _ "o~oo

 ~

**~ 1 1

OJ"CL

' | + JE 1 •*-• D (D Q

.

1

 |

00 Q_ | j— 01 o

——

0)

-Q — 0'oO

 ——

-o

"oo

 ~

~zo. ~— 1 1

_

Dl

CO 0) T)

(D

J

 .C)

w °0) O _

 CD

(N Q.

* JC

1 -*-• D

(D Q_ 00 Q. ^—

o b in o m o in 1

i- o O 0> 0) CO

C3(00) •M•Hd^ (Q+Jco ^.,35+JSE •H•H

,

0) •oo1ooc0"§f

Q>^) ^tr

fe•H

gp '|9A8| puno

s

158
APPENDIX B

REPRESENTATIVE TIME HISTORIES AND NARROWBAND SPECTRA

FOR SELECTED TEST POINTS IN APPENDIX A

This appendix contains plots of the instantaneous time histories and averaged

narrowband spectra for three tip-path-plane angles at a tunnel speed of 70 knots for

the baseline-tip high-twist rotor at all microphone locations. The test points

selected were measured at tip-path-plane angles of -4°, 4°, and 8° to correspond,

respectively, to three angles of interest (onset of BVI noise, maximum BVI noise, and

decreasing BVI noise) at that speed. (See fig. 3.) The time history data have not

been corrected, but the spectra have been corrected for background noise and acoustic

reflections (ref. 15).

159
500

-500

-1OOO

a = -4°

IOOO

5OO

-5OO

-1000

a = 8

.2 .3 .4- .5

Period

.6 .7 .8 .9 1.0

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B1.- Data for baseline-tip high-twist rotor for microphone 1.

V = 70 knots; run 106.

160
m•a

£

10

tn

l)

o

to

110

105

100

95

90

85

80

75

70

125

120

115

110

105

100

95

90

85

80

75

125

120

115

110

105

100

95

90

85

80

75

70

(b)

a = -4°

— 00

a = 8

Averaged spectrum at a = -4°, 4°, and 8°.

Figure B1.- Concluded.

161
1OOO

500

-5OO

-100O

a = -4°

CM

I 1000

CO

<D

5OO

to "

£

a

| -500

8

<-1OOO

1OOO

500

= 4°

i

-500

-1OOO

_ oo

a = 8

O .1 .2 .3 .4- .5 .6 .7 .8 .9 T.O

Period

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B2.- Data for baseline-tip high-twist rotor for microphone 2.

V = 70 knots; run 106.

162
I I I I I I 1 I I I I I I I I I I I I I I I I I I I I I I I I I I I I 60

115

110

105

100

95

90

85

80

75

70

65

a = 8°

2 3 4

Frequency. kHz

(b) Averaged spectrum at a = -4°, 4°, and 8°.

Figure B2.- Concluded.

163
1OOO

5OO

-5OO

CM -10OO

o

= -4°

1OOO

I

500

o

co 0

£

0.

•-H -500

o

< -1OOO

1OOO

5OO

— /to a = 4

-5OO

-10OO

a = 8°

I I

.1 .2 .3 .4- .5

Period

.6 .7 .8 .9 1 .O

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B3.- Data for baseline-tip high-twist rotor for microphone 3.

V = 70 knots; run 106.

164
_ a = -4°

m•a

15

5

a.

•o

3 . 4

Frequency, kHz

(b) Averaged spectrum at o = -4°, 4°, and 8°.

Figure B3.- Concluded.

165
600

300

CM

O

V)

O

<D

V)

CO

2>

Q.

O

-300

•600

6OO

3OO

a = -4

-300

O

< •6OO

6OO

300

-300

-600

a = 4°

_ oo

a = 8

.2. .3 .4 .5 .6

Period

.8 .9 1 .O

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B4.- Data for baseline- tip high-twist rotor for microphone 4.

V = 70 knots; run 106.

166
CO

T3

jj

w

2

QL

O

CO

100

95

90

85

80

75

70

65 [—

60 L

100 p

95

90

85

80

75

70

65

60 L105

100

95

90

85

80

75

70

65

60

a = -4°

,i

— 00

a = 8

IMU I , , i . I

3 4

Frequency, kHz

(b) Averaged spectrum at a = -4°, 4°, and 8°.

Figure B4.- Concluded.

167
6OO

3OO

-3OO

CM

O

a = -4°

a

1

o

1o

-30O

-6OO

6OO

300

a =4'

-3OO

-600

— 00

a = 8

J I i i

O .1 .2 ,3 .4 .5 .6 .7 .8 .9 1 .O

Period

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B5.- Data for baseline-tip high-twist rotor for microphone 5.

V = 70 knots; run 106.

168
I I I l' I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

0 1 2345 6

Frequency, kHz

(b) Averaged spectrum at a = -4°, 4°, and 8°.

Figure B5.- Concluded.

169
3OO

150

CM

-15O

-30O

\

H»wW^

a = -4°

O

O

300 r~

15O -

£

a

.2

CO

o

0

<

-15O

-30O

300

I • 1 • ''11 w

—

a = 4°

1 I 1 I I I 1 I I 1

150 -

-150

-300

.1 .2 .3 .4- .5 .6 .7 .8 .9 1 .O

Period

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B6.- Data for baseline-tip high-twist rotor for microphone 7.

V = 70 knots; run 106.

170
o

TJ

1

95

90

85

80

75

70

65

60

55

100

95

90

85

80

75

70

65

60

105

100

95

90

85

80

75

70

65

a = -4°

. 1

— QO a = 8

234 5

Frequency, kHz

(b) Averaged spectrum at a = -4°, 4°, and 8°.

Figure B6.- Concluded.

171
300

15O

-15O

o

0)

•o

I"

(0

(0

0l_)

a

o

o

o

a =

-150

-3OO

3OO

15O

a = 4°

-15O -

-30O

a = 8(

I i

I I

O .1 .2 .3 .4- .5 .6 .7 .8 .9 1 .O

Period

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B7.- Data for baseline-tip high-twist rotor for microphone 8.

V = 70 knots; run 106.

172
a = -4°

00

TJ

"5

S

o

co

i i i i I i i i i I i i i i I i i i

100

95

90

85

80

75

70

65

60

55

a = 8

3 4

Frequency, kHz

(b) Averaged spectrum at a = -4°, 4°, and 8°.

Figure B7.- Concluded.

173
600

300

-3OO

-6OO

6OO

3OO

O

O

<D

(0

(0

O

«3 -3OO

O

<

a = -4°

a = 4<

-3OO

-600

— 00

a .= 8

.1 .2 .3 .4 .5 .6 .7 .8 .9 1.O

Period

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B8.- Data for baseline-tip high-twist rotor for microphone 9.

V = 70 knots; run 106.

174
CD

TJ

in

<n

£

CL

•u

105

100

95

90

85

80

75

70

65

60

105

100

95

90

85

80

75

70

65

110

105

100

95

90

85

80

75

70

65

a = -4°

a = 8

234 5

Frequency, kHz

6

(b) Averaged spectrum at o = -4°, 4°, and 8C

Figure B8.- Concluded.

175
CM

O

§

I

0

(0

CO

£

a

o

1000

50O

o

-500

-1000

1OOO

5OO

a = -4°

3o

-5OO

-1 OOO

1OOO

5OO

-500

-1OOO

a = 4(

a = 8°

I I

I I

.1 .2 .3 .4- .5 .6

Period

.7 .8 .9 1 .O

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B9.- Data for baseline-tip high-twist rotor for microphone 12.

V = 70 knots; run 106.

176
Ll a = -4°

m•o

1

m

£

o.

90

85

80

75

70

65

110

105

100

95

90

85

80

75

70

65

a = 8

3 4

Frequency. kHz

(b) Averaged spectrum at a= -4°, 4°, and 8°.

Figure B9.- Concluded.

177
600

300

-300

-600

600

300

CM

O

8

I

£

CO<o o

a

o

'fj -300

O

O

<

 -6OO

6OO

3OO

a = -4°

— /to a = 4

-3OO

-6OO

"^j^^

— 00

a = 8

.1 .2 .3 .4- .5 .6

Period

.7 .8 .9 1.0

(a) Acoustic time history at a = -4°, 4°, and 8°.

Figure B10.- Data for baseline-tip high-twist rotor for microphone 17.

V = 70 knots; run 106.

178
-a = -4°

J

m

T3

110

105

100

95

90

85

80

75

70

65

60

- a = 8 _ 00

2 3 4

Frequency. kHz

(b) Averaged spectrum at a = -4°, 4°, and 8°.

Figure B10.- Concluded.

179
Standard Bibliographic Page

1. Report No.

NASA TM-87698

2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle

Wind-Tunnel Acoustic Results of Two Rotor Models

With Several Tip Designs

5. Report Date

July 1986

6. Performing Organization Code

532-06-13-06

7. Author(s)

R. M. Martin and Andrew B. Connor

8. Performing Organization Report No.

L-16081

9. Performing Organization Name and Address

NASA Langley Research Center

Hampton, VA 23665-5225

10. Work Unit No.

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, DC 20546-0001

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

A three-phase research program has been undertaken to study the acoustic signals

due to the aerodynamic interaction of rotorcraft main rotors and tail rotors.

During the first phase, two different rotor models with several interchangeable

tips were tested in the Langley 4- by 7-Meter Tunnel on the U.S. Army rotor

model system. An extensive acoustic data base was acquired, with special

emphasis on blade-vortex interaction (BVI) noise. The details of the experimental procedure, acoustic data acquisition, and reduction are documented. The

overall sound pressure level (OASPL) of the high-twist rotor systems is relatively insensitive to flight speed but generally increases with rotor tip-pathplane angle. The QASPL of the high-twist rotors is dominated by acoustic energy

in the low-frequency harmonics. The OASPL of the low-twist rotor systems shows

more dependence on flight speed than the high-twist rotors, in addition to being

quite sensitive to tip-path-plane angle. An integrated band-limited sound

pressure level, limited by 500 to 3000 Hz, is a useful metric to quantify the

occurrence of BVI noise. The OASPL of the low-twist rotors is strongly influenced by the band-limited sound levels, indicating that the blade-vortex impulsive noise is a dominant noise source for this rotor design. The midfrequency

acoustic levels for both rotors show a very strong dependence on rotor tip-pathplane angle. The tip-path-plane angle at which the maximum midfrequency sound

level occurs consistently decreases with increasing flight speed. The maximum

midfrequency sound level measured at a given location is constant regardless of

the flight speed.

17. Key Words (Suggested by Authors(s))

Rotor acoustics

Blade-vortex interaction noise

Rotor noise

Rotor tips

18. Distribution Statement

Unclassified - Unlimited

Subject Category 71

19. Security Classif.(of this report)

Unclassified

20. Security Classif.(of this page)

Unclassified

21. No. of Pages

182

22. Price

A09

For sale by the National Technical Information Service, Springfield, Virginia 22161

NASA-Langley, 1986