Brenda S. Henderson and Mark P. Wernet

Glenn Research Center, Cleveland, Ohio

A PIV Study of Slotted Air 

Injection For Jet Noise Reduction

NASA/TM—2012-217251

May 2012

AIAA–2011–8665
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Brenda S. Henderson and Mark P. Wernet

Glenn Research Center, Cleveland, Ohio

A PIV Study of Slotted Air 

Injection For Jet Noise Reduction

NASA/TM—2012-217251

May 2012

AIAA–2011–8665

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

17th Aeroacoustics Conference

cosponsored by the American Institute of Aeronautics and Astronautics and 

the Confederation of European Aerospace Societies

Portland, Oregon, June 5–8, 2011
Acknowledgments

The authors thank the engineers and technicians in the LSAWT and the AAPL for assisting with the experiments. The nozzles 

were designed in cooperation with Goodrich Aerostructures. The authors thank Alan Douglas and Harry Haskin for leading the 

mechanical design. This work was supported by the Subsonic Fixed Wing Project and Supersonics Project in the Fundamental 

Aeronautics Program. 

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Trade names and trademarks are used in this report for identification 

only. Their usage does not constitute an official endorsement, 

either expressed or implied, by the National Aeronautics and 

Space Administration.

This work was sponsored by the Fundamental Aeronautics Program 

at the NASA Glenn Research Center.

Level of Review: This material has been technically reviewed by technical management. 
A PIV Study of Slotted Air Injection For Jet Noise Reduction 

Results from acoustic and Particle Image Velocimetry (PIV) measurements are presented 

for single and dual-stream jets with fluidic injection on the core stream. The fluidic 

injection nozzles delivered air to the jet through slots on the interior of the nozzle at the 

nozzle trailing edge. The investigations include subsonic and supersonic jet conditions. 

Reductions in broadband shock noise and low frequency mixing noise were obtained with 

the introduction of fluidic injection on single stream jets. Fluidic injection was found to 

eliminate shock cells, increase jet mixing, and reduce turbulent kinetic energy levels near the 

end of the potential core. For dual-stream subsonic jets, the introduction of fluidic injection 

reduced low frequency noise in the peak jet noise direction and enhanced jet mixing. For 

dual-stream jets with supersonic fan streams and subsonic core streams, the introduction of 

fluidic injection in the core stream impacted the jet shock cell structure but had little effect 

on mixing between the core and fan streams. 

I. Introduction 

ANY jet noise reduction concepts such as mechanical chevrons (serrations at the nozzle trailing edge that 

deflect into the flow) rely on enhanced jet mixing for noise reduction. Most of these devices are passive and 

remain deployed throughout the aircraft mission introducing thrust losses during all phases of operation. An 

attractive alternative is the fluidic chevron produced by injected air at the nozzle trailing edge that is deployed only 

when needed, thus limiting overall performance penalties. However, fluidic injection systems are plagued with 

implementation challenges most commonly in the form of high pressure air requirements (often in excess of 700 

kPa). While these high-pressure systems allow for noise reduction with realistic injection mass flow rates (on the 

order of a fraction of a percent of the core mass flow rate), the required pressures are well beyond those currently 

available on aircraft1

. Modifications to the jet plume and the impact on far-field noise as a result of high-pressure 

injection is relatively well understood due to the large number of acoustic and flow-field studies presented in the 

literature2,3. Conversely, low pressure injection systems have received little attention with only a few studies 

investigating noise reduction potential4,5. Accompanying flow-field studies are non-existent and, therefore, the 

injection-jet plume interaction process is not well understood. The current study uses Particle Image Velocimetry 

(PIV) to investigate jet plume modifications produced by a low-pressure air injection system with slotted injectors. 

 A jet injected into cross flow (the main jet) produces a counter-rotating vortex pair6

. The vortex pair is bent by 

the main jet and produces a longitudinal vortex pair. For multiple injectors, the impact of the injected flow on the 

main jet depends on the injection system configuration and operating pressure. For high-pressure (often in excess of 

700 kPa) injection systems with multiple circular injectors (often referred to as microjets), the longitudinal vortex 

pairs transfer low-momentum ambient fluid to the high-momentum main jet2

. Increases in potential core length with 

the introduction of microjets have been reported7,8 (indicating reduced mixing compared to that of the baseline case) 

and are an indication that noise reduction is achieved through a different mechanism than that associated with the 

mechanical chevron. Decreased7,8,9 and increased3,10 (over that of the baseline jet) peak turbulence levels have been 

reported for microjet injection with the apparent discrepancy in reported results due to the measurement location and 

the injection system configuration and operating pressure. For slotted injection systems using pressures below those 

often used in microjets, only numerical studies have investigated the injector-main jet interaction11,12. These studies 

have shown that the length of the main jet potential core is reduced by the introduction of fluidic injection12, a result 

indicating that slotted, low-pressure injectors may reduce noise through a mechanism (enhanced mixing) related to 

that of the mechanical chevron. However, experiments are needed to validate these numerical studies. 

M 

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Brenda S. Henderson and Mark P. Wernet 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 
 Previous investigations with low-pressure systems have shown that noise reduction can be achieved in dual 

stream subsonic jets and single stream supersonic jets. For dual-stream jets, noise reduction is achieved with core 

and a combination of core and fan-stream injectors5,13 (for both circular and slotted injectors). For single stream 

supersonic jets, fluidic injection reduces broadband shock noise14. Limited benefit has been found with fluidic 

injection used on dual-stream jets with supersonic fan streams and transonic core streams14. Flow-field data are 

required to fully understand the impact of the fluidic chevrons on the jet plume and the resulting acoustic radiation. 

 The current study uses two-component and stereo PIV to investigate the impact of slotted, low-pressure, fluidic 

injection on subsonic and supersonic jets. Single and dual-stream jets are investigated. 

II. Experimental Approach 

The acoustic experiments were conducted in the Low Speed Aeroacoustic Wind Tunnel (LSAWT) at the NASA 

Langley Research Center shown in Fig. 1. A 1.4 m x 1.4 m square tunnel nozzle exhausts into a 10.4 m long test 

cell with a 5.2 m x 5.2 m cross section, providing a simulated flight stream with Mach numbers up to 0.32. The 

floor, ceiling, and walls are covered with fiberglass wedges. The Jet Engine Simulator (JES) located in center of the 

flight stream, consists of co-annular streams used to simulate the exhaust of core and fan stream turbo-fan engines. 

Each stream is equipped with an electric pre-heater and a propane-fired, sudden-expansion burner to achieve engine 

temperatures of commercial and military aircraft engines. 

The acoustic results presented here were obtained from a 28-microphone sideline array located 3.7 m from the 

centerline of the JES (see Fig. 1). Microphone calibrations including sensitivity, actuator, and diffraction 

corrections have been made. In addition, the data have been corrected for shear layer effects using Amiet’s 15

corrections and for atmospheric absorption16. The narrowband spectra have a bandwidth of 25.63 Hz and are 

presented for the FAA noise certification reference conditions (1atm, 77o

F, 70% relative humidity). 

The PIV experiments were conducted in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn 

Research Center shown in Fig. 2. The AAPL is a 20 m radius geodesic dome treated with acoustic wedges. Within 

the AAPL is the Nozzle Acoustic Test Rig (NATR) which produces a 1.3 m diameter simulated forward flight 

stream (free jet) reaching Mach numbers of 0.35 and contains the High Flow Jet Exit Rig (HFJER), a dual-stream jet 

engine simulator capable of replicating most commercial turbo-fan engine temperatures and pressures.17

A representative 1/9th scale, bypass ratio (BPR) 5 nozzle system with a pylon and external plug was used in the 

experiments (see Fig. 3). Three core nozzles (two air injection nozzles and one baseline nozzle) each with a 

diameter equal to 12.9 cm and an area equal to 70.8 cm2

 and a 24.0 cm fan nozzle with an area equal to 188 cm2

were used in the study. For each air injection nozzle, air was delivered to a common plenum in the nozzle through a 

tube embedded in the pylon as shown in Fig. 4. Six contoured injection passages downstream of the plenum were 

used to deliver air to injection slots at the trailing edge of the nozzle. The slots were on the core stream side of the 

nozzle allowing air to exhaust into the core stream. One of the air injection nozzles (identified as the “steep” 

injection nozzle) and had an injection angle (angle between the injection passage and the core nozzle flow at the 

nozzle trailing edge) of 45 and the other air injection nozzle (identified as the “shallow” injection o

injection angle of 15o

. The trailing edge thicknesses of the injection nozzles were non-uniform due the injection 

passages as shown in Fig. 3. The baseline core nozzle had a uniform trailing edge thickness of 0.9 mm and no 

injection passages. The angle between the pylon and microphone axis was equal to 122o

 for all acoustic 

experiments. 

Two types of PIV experiments were conducted: (1) two-component streamwise experiments and (2) cross-stream 

stereo PIV experiments. For all PIV studies, Redlake ES11000 cameras with 2.6K x 4K CCD arrays were used to 

record images. For the streamwise experiments, two cameras, each with a 380 mm x 325 mm field of view, were 

used in a side-by-side configuration with a 28 mm overlap between camera images. The laser light sheet (created 

with a 400mJ per pulse, 532 nm, dual-head Nd-YAG laser) illuminated the jet centerline and was traversed 

downstream incrementally to image a total of 18 core nozzle diameters. Figure 5 shows the two light sheet 

orientations used in the experiments. For the core air injection nozzles, light-sheet orientation 1 passed through one 

injection port on the side opposite to the pylon. The light sheet was located slightly behind (relative to the camera 

viewing side of the jet) the tip of the pylon for light sheet orientation 2 and no injection passages were illuminated. 

In the cross-stream experiments, the laser light sheet illuminated cross-stream planes in the jet and images were 

acquired at 1.2D, 1.6D, 2D, 2.4D, 3.4D, 4.4D, 5.4D, 7.8D, 10.3D, 13.2D, and 16D downstream of the core nozzle 

trailing edge where D is the diameter of the core nozzle. Only the lower half of the jet was imaged due to the pylon 

obstructing images near the nozzle exit. The first cross-plane (1.2D) was just downstream of the nozzle plug. The 

field of view for the cameras was 400 mm x 325 mm. For all PIV experiments, the core stream, fan stream, and 

injection flow were seeded with 0.7Pm aluminum oxide particles. The core and fan streams were seeded using a pH 

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nozzle) had an 
stabilized dispersion of aluminum oxide in ethanol. The air injection stream was seeded using a fluidized bed. The 

free jet flight stream was seeded with Rosco Delta 3000 foggers with 0.25 – 0.6 Pm particles. 

 For the stereo PIV experiments, the 2-D vector maps from the Left and Right cameras were generated using a 

multi-pass processing approach. The processing strategy used an initial pass with 64x64 pixel subregions on 32 

pixel centers followed by 6 passes (using simulated annealing) at 32x32 pixel subregions on 16 pixel centers, 

followed by two final passes using subregion distortion processing. Symmetric Phase Only Filtering was used on 

the cross-stream data sets to reduce the effect of flare light from the model. 

 All PIV surveys used 400 image pairs per axial station, yielding 400 velocity vector maps at each axial station. 

The velocity vector maps were then ensemble averaged to compute the first and second order statistics. Hard 

velocity cutoff limits and Chauvenet’s Criteria were used to remove outliers. 

 The conditions used in the experiments are shown in Table 1. The Nozzle Pressure Ratio (NPR) is the ratio of 

the stagnation pressure of the jet to the ambient pressure. The Total Temperature Ratio (TTR) is the ratio of the 

total temperature of the jet to the ambient temperature. Subscripts “c” and “f” refer to the core and fan streams, 

respectively. The Mach number is given by M. The single stream experiments were conducted with the core stream 

at the indicated conditions and the fan stream at conditions equal to that of the flight stream. The dual high subsonic 

stream experiments were conducted at representative takeoff conditions. The dual stream supersonic fan stream and 

subsonic core stream experiments were conducted at conditions representative of those that occur for some 

commercial aircraft at cruise. While free jet Mach numbers (Mfj) equal to 0.1 and 0.28 were used in the 

experiments, only data for M = 0.1 are presented here. fj

III. Results 

A. Single Low Supersonic Core Stream Experiments 

The acoustic spectra acquired for a single supersonic stream are shown in Fig. 6 for a range of Injection Pressure 

Ratios (IPR), the ratio of the injected flow stagnation pressure to the ambient pressure. Observation angles greater 

than 90o

 are in the downstream direction relative to the nozzle exit. For supersonic operating conditions, the 

baseline data are acquired with the air injection nozzles with no injection flow (IPR = 1.0) since the injection 

nozzles produced slightly different broadband shock noise levels than the baseline nozzle presumably due to slight 

differences in the core nozzle external contours. As shown in Fig. 6 (a), the broadband shock noise levels decrease 

as IPR increases. In the peak jet noise direction [see Fig. 6(b)], low frequency broadband levels decrease as IPR 

increases. 

Streamwise velocity contours obtained from PIV experiments for the same conditions as those in Fig. 6 are 

shown in Fig. 7 for laser light sheet orientation 2. Quasi-periodic shock cells can be seen in the core flows for IPR = 

1.0 and 2.0. The shock cells disappear for IPR = 4.0 which explains the elimination of broadband shock noise in 

the corresponding spectrum in Figs. 6 (a). Similar results to those shown in Fig. 7 were obtained for laser light-sheet 

orientation 1. 

Turbulent Kinetic Energy (TKE) contour plots obtained from the streamwise PIV experiments for the same 

conditions as those in Fig. 6 are shown in Figs. 8 and 9 for light sheet orientations 1 and 2, respectively. For the 

TKE calculations, the out-of-plane component of the velocity fluctuation is assumed equal to that of the transverse 

component measured in the PIV experiments. For laser light-sheet orientation 1, TKE is higher for the no injection 

case (IPR = 1.0) than for flow with injection (IPR = 2.0 and 4.0). For light-sheet orientation 2, TKE levels near the 

end of the potential core decrease with increasing IPR. The lower TKE levels (and corresponding shorter potential 

core length) for IPR = 2.0 and 4.0 (relative to IPR = 1.0) are consistent with the corresponding noise reduction levels 

shown in Fig. 6 (b). Near the nozzle trailing edges in light-sheet orientation 2, the highest turbulent kinetic energy 

occurs for IPR = 4.0, a result consistent with the increased high frequency noise (relative to IPR = 1.0) in Fig. 6 (a) 

for the same IPR. 

 Streamwise velocity contours and corresponding streamwise vorticity contours with cross-stream velocity 

vectors obtained from the stereo PIV experiments are shown in Figs. 10 and 11, respectively. The contour levels in 

Fig. 10 are the same as those in Fig. 7. White regions in the contour plots are regions where few images were used 

in the ensemble averages due to a lack of correlation from many of the PIV image pairs as a result of flare from 

nozzle surfaces. The vorticity contours are an exploded view as shown in Fig. 11. Enlarged pairs of velocity 

vectors along with red arrows indicating regions of injected flow are shown in the first contour plot of Fig. 11 for 

clarity. The fluidic injectors create streamwise counter-rotating vortex pairs (shown as high vorticity levels in Fig. 

11) that draw ambient flow into the core flow creating “lobes” in the core stre am flow [see Figs. 10 (b) and (c)] and 

enhancing the mixing between the core stream and ambient flow. Increasing IPR increases peak vorticity levels and 

jet mixing within the first three diameters downstream of the nozzle exit. 

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B. Dual High Subsonic Stream Experiments 

The acoustic spectra acquired at the dual high subsonic stream conditions (representative takeoff conditions) in 

Table 1 are shown in Fig. 12 and Fig. 13 for the steep and shallow injectors, respectively. For subsonic jet flows,

the baseline data are taken with the baseline nozzle. For steep injectors, increasing IPR increases high frequency 

noise relative to the baseline nozzle at a 90o

 observation angle [see Fig. 12 (a)]. In the peak jet noise direction, the 

introduction of air injection decreases low frequency noise. The acoustic spectra produced by the baseline nozzle 

and the shallow injectors with IPR = 3.2 are similar (see Fig.13) although the shallow injectors produce slight low 

frequency noise reduction in the peak jet noise direction relative to the baseline nozzle. 

Streamwise velocity contours obtained from the streamwise PIV experiments for the baseline, steep fluidic 

injection, and shallow fluidic injection nozzles are shown in Fig. 14 for the same jet conditions as those used in Figs.

12 and 13. Data for the baseline nozzle were only obtained for laser light-sheet orientation 2 since this orientation 

captured two areas of flow extremes: (1) downstream of the pylon where turbulence levels usually peak and (2) on 

the side of the jet opposite to the pylon where the pylon effects on the jet are a minimum. Data for the shallow 

fluidic injection nozzle and laser light-sheet orientation 2 were not acquired due to testing time constraints. For the 

steep fluidic injection nozzle, the length of the primary potential core decreases as the injection pressure ratio 

increases indicating increased mixing with increased IPR. For the shallow fluidic injection nozzle, the primary 

potential core length is shorter than that for the baseline nozzle but longer than that for the steep fluidic injection 

nozzle operated at the same IPR. The larger noise reductions for the steep injection nozzle than for the shallow 

injection nozzle relative to the baseline nozzle [see Figs. 13 (b) and 14 (b)] are most likely associated with the 

greater mixing rate of the steep injectors than the shallow injectors. 

Turbulent kinetic energy contour plots for the same conditions as those in Fig. 14 are shown in Fig. 15. Since 

data for the shallow injectors were only obtained for light-sheet orientation 1, results for both light-sheet orientations 

have been included for the steep fluidic injector to allow for comparisons between the two types of injectors. The 

highest TKE levels occur for the baseline nozzle downstream of the pylon. The peak TKE level for the steep fluidic 

injection nozzle is higher than that for the shallow fluidic injection nozzle at the same IPR using the same light-sheet 

orientation (orientation 1). 

Streamwise velocity contours and corresponding streamwise vorticity contours with cross-stream velocity vectors 

obtained from the stereo PIV experiments are shown in Figs. 16 and 17, respectively. The asymmetry in the lower 

center region of the baseline nozzle core stream is the result of a bifurcator in the fan stream upstream of the nozzle 

trailing edge. As in the case of the single stream experiments, the fluidic injectors create streamwise counterrotating vortex pairs that draw surrounding fluid (fan stream flow) into the core flow and enhance mixing between 

the two streams. The effects of the pylon (and possibly the upstream fan-stream bifurcator) may impact vortex 

development with downstream distance and result in the lack of vortex pair strength symmetry. The influence of the 

vortex pairs on the core and fan stream flows appears to extend much further downstream for the slotted injectors 

used in these experiments than for microjet injectors used by Refs. 2 and 3. Although not evident in Fig. 18 due to 

selecting a maximum vorticity contour level well below the maximum vorticity level near the nozzle exit (for clarity 

at cross-stream locations where vorticity levels are low), the peak vorticity levels produced by the steep injection 

nozzle are higher for IPR = 3.2 than for IPR = 2.4 within the first three core jet diameters resulting in greater mixing 

for IPR = 3.2 than for IPR = 2.4 jet. However, vorticity levels decay more rapidly for IPR = 3.2 than for IPR = 2.4 at 

axial locations greater than three jet diameters. The peak vorticity levels for the steep and shallow injectors at the 

same IPR are very similar for the first three core jet diameters although the spatial extent of vorticity is slightly 

different for the two flows. 

C. Low Supersonic Fan Stream with Subsonic Core Stream Experiments 

The acoustic spectra for dual-stream jets with supersonic fan streams and subsonic core streams at a free jet Mach 

number equal to 0.10 are shown in Fig. 18. The steep fluidic injection nozzle was used for the core flow and IPR = 

1.0 was used for the baseline data. The introduction of injected flow reduces broadband shock noise but has little 

effect on mixing noise. Experiments conducted at higher nozzle pressure ratios (NPRf = 2.36 and NPRc = 1.82) 

showed that fluidic injection had no broadband shock or mixing noise reduction benefits relative to the no-injection 

case. 

Streamwise velocity contours obtained at the same jet conditions as those in Fig. 18 are shown in Fig. 19 for laser 

light-sheet orientation 2. Shock cells can be seen in the fan stream of both jet plumes (IPR = 1.0 and 3.0) on the side 

of the jet opposite to the pylon although higher levels of injection (IPR = 3.0) reduce the axial extent of the shock 

cells. Similar results were obtained for laser light-sheet orientation 1. The inability to eliminate shock cells with 

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fluidic injection at least partially explains the inability to eliminate broadband shock noise with fluidic injection [see 

18 (a)]. 

 Streamwise velocity contours and corresponding streamwise vorticity contours with cross-stream velocity vectors 

obtained from the stereo PIV experiments are shown in Figs. 20 and 21, respectively. The impact of the injection 

passages can be seen in the fan stream flow for the no injection case (IPR = 1.0). For IPR = 3.0, the core stream 

“lobes” associated with counter rotating vortex pairs are observed but produce limited o r no mixing between the fan 

and free-jet streams (possibly explaining the lack of mixing noise reduction in Fig. 18 for IPR = 3.0 relative to IPR = 

1.0). The distortion of the fan-core shear layer may account for the decrease in the shock train length for IPR = 3.0 

relative to IPR = 1.0. The corresponding vorticity plots in Fig. 21 show that the injection passages in the no 

injection case (IPR = 1.0) produce vorticity of the opposite sign to that of the injected flow with IPR = 3.0. For the 

supersonic fan stream and subsonic core stream, the vorticity associated with the injected flow has little effect on the 

fan stream which most likely explains the lack of noise reduction observed in Fig. 18 for IPR = 3.0 (relative to the 

no injection case). 

 

IV. Discussion and Conclusions 

Experiments conducted with a fluidic nozzle for a single, supersonic jet show the potential for fluidic injection to 

reduce broadband shock noise and low frequency mixing noise. Reductions in peak TKE near the end of the 

potential core and enhanced mixing are also achieved with the introduction of fluidic injection. 

The introduction of fluidic injection in the core stream of a dual stream jet at a representative commercial takeoff 

condition results in low frequency noise reduction in the peak jet noise direction with slight increases in high 

frequency noise at 90o

. Fluidic injection reduces (relative to the baseline nozzle) TKE levels downstream of the 

pylon near the end of the primary potential core. The influence of counter-rotating vortex pairs produced by the 

injected flow on the core and fan streams appears to extend further downstream than that produced by microjet 

injectors [see Refs. 2 and 3]. 

The introduction of fluidic injection on the core stream of a dual stream jet with a supersonic fan stream and a 

subsonic core stream can reduce broadband shock noise but has no mixing noise benefit. Particle image velocimetry 

studies show that, for this flow regime, fluidic injection has little impact on the fan stream. 

References 1 Henderson, B. “Fifty years of fluidic injection for jet noise reduction,” International J. Aeroacoustics, Vol. 9, pp. 91 – 122, 

2010. 2

Alkisler, M. B., Krothapalli, A., and Butler, G. W. “The effect of streamwise vortices on the aeroacoustics of a Mach 0.9 

jet,” J. Fluid Mech. 578, pp. 139 – 169, 2007. 3

Alkislar, M. B. “Aeroacoustics of a Mach 0.9 jet with chevron-microjet combination,” AIAA-2008-3041, 2008. 4

Henderson, B., Kinzie, K., Whitmire, J., and Abeysinghe, A. “Aeroacoustic improvements of fluidic chevron nozzles,” 

AIAA-2006-2706, 2006. 5

Harrison, S., Gutmark, E., and Martens, S. “Jet noise reduction by fluidic injection on a separate flow exhaust system,” 

AIAA-2007-439, 2007. 6

Margason, R. “Fifty years of jet in cross-flow research,” AGARD Meeting on Computational and Experimental Assessment 

of Jets in Cross Flow, April 1993, N94-28004, 1993. 7

Arakeri, V. H., Krothapalli, A., Siddavaram, V., Alkislar, M. B., and Lourenco, L. M. “On the use of microjets to suppress 

turbulence in a Mach 0.9 axisymmetric jet,” J. Fluid Mech. 490, 75-98, 2003. 8

Laurendeau, E., Bonnet, J. P., Jordan, P., and Delville, J. “Impact of fluidic chevrons on the turbulence structure of a 

subsonic jet, AIAA-2006-3510, 2006. 9

Callender, B., Gutmark, E., and Martens, S. “A comprehensive study of fluidic injection technology for jet noise reduction,” 

AIAA-2007-3608, 2007. 10Alkislar, M. B., Krothapalli, A., Lourenco, L. M. and Butler, G. W. “The effect of streamwise vorticity on the 

aeroacoustics of Mach 0.9 axisymmetric jet,” AIAA-2005-3045, 2005. 11Chauvet, N., Deck, S., and Jacquin, L. “Zonal detached eddy simulation of a controlled propulsive jet,” AIAA J. 45 [10], 

2458-2473, 2007. 12Kinzie, K., Henderson, B., Whitmire, J., Abeysinghe, A. (2004). “Fluidic chevrons for jet noise reduction,” ACTIVE 04, 

Williamsburg, Virginia, September 20 – 22, 2004. 13Henderson, B., Kinzie, K., Whitmire, J., and Abeysinghe, A. “Aeroacoustic improvements of fluidic chevron nozzles,” 

AIAA-2006-2706, 2006. 14Henderson, B. and Norum, T. “Impact of fluidic chevrons on supersonic jet noise,” AIAA-2007-3595, 2007. 15Amiet, R. K., “Correction of open jet wind tunnel measurements for shear layer refraction,” AIAA-77-54, 1977. 

16ANSI S1.26-1995 (R2004), “Method for calculation of absorption of sound by the atmosphere,”. 

17Soeder, R., Wnuk, S., and Loew, R. “Aero -Acoustic Propulsion Laboratory Nozzle Acoustic Test Rig User Manual,” 

NASA/TM-2006-212939, 2006. 

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Microphone Array

JES

Tunnel Nozzle

Collector

Figure 1. A schematic of the Low Speed Aeroacoustics Wind Tunnel (LSAWT) and the 

Jet Engine Simulator (JES).

Figure 2. A photograph of the AeroAcoustic Propulsion Laboratory (AAPL) 

showing the Nozzle Acoustic Test Rig 

(NATR).

NATR

Microphone 

Array

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Figure 4. A schematic of the air delivery system for the air injection 

nozzles.

Slotted core nozzle

Fan Nozzle

Pylon

Fluidic Chevron Core Nozzle

Air Supply

Figure 5. The laser lightsheet orientations used in the 

streamwise PIV experiments.

Light-Sheet 

Orientation 1

Light-Sheet 

Orientation 2

NPRc TTRc NPRf TTRf Experiment

2.18 1.06 1.01 1.00 Single Low Supersonic Core Stream

1.56 2.66 1.75 1.16 Dual High Subsonic Streams

 Low Supersonic Fan Stream with 

Subsonic Core Stream 1.61 2.13 2.24 1.05

Table 1 Experimental Operating Conditions

Figure 3. The air injection nozzle system used in acoustic and PIV experiments.

Fan Nozzle

Pylon

Steep Core Injection Nozzle

Injectors

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Broadband Shock Noise

Figure 6. Narrowband spectra acquired for a single stream supersonic jet using the steep fluidic injection core 

nozzle for observation angles equal to (a) 90o and (b) 150o

.

(a) (b)

Steep Injectors

IPR = 2.0

1.5D

Steep Injectors

IPR = 1.0

Core Nozzle Trailing Edge

Fan Nozzle Trailing Edge

Pylon

Plug

Figure 7. Streamwise velocity contours obtained from the streamwise PIV experiments with laser light-sheet 

orientation 2 for the conditions in Fig. 6.

Steep Injectors

IPR = 4.0

Pylon

Plug

1$6$702 
Steep Injectors

IPR = 4.0

Steep Injectors

IPR = 2.0

Figure 9. Turbulent kinetic energy contours for the conditions in Fig. 6 obtained for the streamwise PIV 

experiments with laser light-sheet orientation 2. The legend is the same as that used in Fig. 8.

Steep Injectors

IPR = 1.0

Increased turbulence relative to IPR = 1.0

Steep Injectors

IPR = 1.0

Steep Injectors

IPR = 2.0

Steep Injectors

IPR = 4.0

Figure 8. Turbulent kinetic energy contours obtained for the streamwise PIV experiments with laser light-sheet 

orientation 1 for the conditions in Fig. 6.

TKE

1$6$702 
(b)

D D D D D

Figure 11. An exploded view of the streamwise vorticity contours and cross-stream velocity vectors 

obtained in the cross-stream planes indicated in the plots for (a) the steep injection nozzle with IPR = 2.0 

and (b) the steep injection nozzle with IPR = 4.0.

(a)

Fluidic Injection Location Fluidic Injection Location

(b)

(a)

Figure 10. Streamwise velocity contours obtained in the cross-stream planes indicated in the plots for (a) the 

steep injection nozzle with IPR = 1.0, (b) the steep injection nozzle with IPR = 2.0, and (c) the steep injection 

nozzle with IPR = 4.0. The legend is the same as that used in Fig. 7

D D D D

(c)

1$6$702 

1.2 1.6 2.0D 2.4 3.4

1.2 1.6 2.0 2.4 3.4
Figure 12. Narrowband spectra acquired at a representative takeoff condition using the baseline and steep 

fluidic injection nozzles for observation angles equal to (a) 90o and (b) 150o

.

(a) (b)

Figure 13. Narrowband spectra acquired at a representative takeoff condition using the baseline and shallow

fluidic injection nozzles for observation angles equal to (a) 90o and (b) 150o

.

(a) (b)

1$6$702 
Figure 14. Streamwise velocity contours obtained from the streamwise PIV experiments for the jet conditions 

in Figs. 12 and 13.

Baseline

Laser Light-Sheet Orientation 2

Steep Injectors

IPR = 2.4

Laser Light-Sheet Orientation 2

Steep Injectors

IPR = 3.2

Laser Light-Sheet Orientation 2

Steep Injectors

IPR = 3.2

Laser Light-Sheet Orientation 1

Shallow Injectors

IPR = 3.2

Laser Light-Sheet Orientation 1

1$6$702 
Figure 15. Turbulent kinetic energy contours obtained from the streamwise PIV experiments for 

the jet conditions in Figs. 12 and 13.

Baseline

Laser Light-Sheet Orientation 2

Steep Injectors

IPR = 2.4

Laser Light-Sheet Orientation 2

Steep Injectors

IPR = 3.2

Laser Light-Sheet Orientation 2

Steep Injectors

IPR = 3.2

Laser Light-Sheet Orientation 1

Shallow Injectors

IPR = 3.2

Laser Light-Sheet Orientation 1

TKE

1$6$702 
D D D D D

(d)

Figure 16. Streamwise velocity contours obtained in the cross-stream planes indicated in the plots at the jet 

conditions in Figs. 12 and 13 for (a) the baseline nozzle (b) the steep injection nozzle with IPR = 2.4, (c) the 

steep injection nozzle with IPR = 3.2, and (d) the shallow injection nozzle with IPR = 3.2. The legend is the 

same as that used in Fig. 14

(a)

(b)

(c)

Figure 17. An exploded view of the streamwise vorticity contours and cross-stream velocity vectors 

obtained in the cross-stream planes indicated in the plots for the jet conditions in Figs. 12 and 13 for (a)

the steep injection nozzle with IPR = 2.4, (b) the steep injection nozzle with IPR = 3.2, and (c) the shallow 

injection nozzle with IPR = 3.2.

(b)

(c)

D D D D D

Fluidic Injection Location Fluidic Injection Location (a)

1$6$702 

1.2 1.6 2.0 2.4 3.4

1.2 1.6 2.0 2.4 3.4
(a)

Figure 18. Narrowband spectra acquired for a dual stream jet with a supersonic fan stream and a subsonic core 

stream using the steep fluidic injection nozzle for observation angles equal to (a) 90o and (b) 150o

.

(a) (b)

Figure 19. Streamwise velocity contours obtained from the streamwise PIV experiments for the jet

conditions in Fig. 18 and laser light-sheet orientation 2.

Steep Injectors

IPR = 1.0

Steep Injectors

IPR = 3.0

1$6$702 
Figure 20. Streamwise velocity contours obtained in the cross-stream planes indicated in the plots 

at the jet conditions in Fig. 18 for the steep injection nozzle with (a) IPR = 1.0 and (b) IPR = 3.0. 

The legend is the same as that used in Fig. 19

(a)

2D D D D D

(b)

Figure 21. An exploded view of the streamwise vorticity contours and cross-stream velocity 

vectors obtained in the cross-stream planes indicated in the plots at the jet conditions in Fig. 

18 for the steep injection nozzle with (a) IPR = 1.0 and (b) IPR = 3.0. The legend is the same 

as that used in Fig. 17.

(a)

(b)

D D D D D

1$6$702 

1.2 1.6 2.0 2.4 3.4

1.2 1.6 2.0 2.4 3.4

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1. REPORT DATE (DD-MM-YYYY)

01-05-2012 

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4. TITLE AND SUBTITLE

A PIV Study of Slotted Air Injection For Jet Noise Reduction 

5a. CONTRACT NUMBER

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6. AUTHOR(S)

Henderson, Brenda, S.; Wernet, Mark, P. 

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WBS 984754.02.07.03.17.05 

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National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field 

Cleveland, Ohio 44135-3191 

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Available electronically at http://www.sti.nasa.gov 

This publication is available from the NASA Center for AeroSpace Information, 443-757-5802

13. SUPPLEMENTARY NOTES

14. ABSTRACT

Results from acoustic and Particle Image Velocimetry (PIV) measurements are presented for single and dual-stream jets with fluidic 

injection on the core stream. The fluidic injection nozzles delivered air to the jet through slots on the interior of the nozzle at the nozzle 

trailing edge. The investigations include subsonic and supersonic jet conditions. Reductions in broadband shock noise and low frequency 

mixing noise were obtained with the introduction of fluidic injection on single stream jets. Fluidic injection was found to eliminate shock 

cells, increase jet mixing, and reduce turbulent kinetic energy levels near the end of the potential core. For dual-stream subsonic jets, the 

introduction of fluidic injection reduced low frequency noise in the peak jet noise direction and enhanced jet mixing. For dual-stream jets 

with supersonic fan streams and subsonic core streams, the introduction of fluidic injection in the core stream impacted the jet shock cell 

structure but had little effect on mixing between the core and fan streams.

15. SUBJECT TERMS

PIV; Slotted; Air injection; Jet noise reduction 

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