Flow and Acoustics of Jets from Practical Nozzles for High-Performance Military Aircraft

Flow and Acoustics of Jets from Practical Nozzles for High-

Performance Military Aircraft

University of Cincinnati29 October 2010Cincinnati, Ohio

Ph.D. Dissertation

submitted to the Department of Aerospace Engineering

by David E. Munday

1

Outline

• Introduction• Background• Methodology• Results

– Baseline– Chevrons– Microjets

• Summary• Recommendations• Acknowledgements

2

Outline




3

The problem•

Military aircraft noise effects communities around military bases•

$34.4 Million settlement from one law suit for one base•

Political pressure limits training and testing

•Noise leads to health issues for personnel who work around military aircraft•

More then $750 Million in hearing-loss disability payments in ‘05

4

35° 150°100°

From Subsonic to Supersonic Jets

Supersonic, underexpanded

• Lots of work has already been done on subsonic jets

• Several noise reduction techniques have been explored

• Supersonic jets bring additional physics (shocks)

• Additional noise production mechanisms (shock related)

• Application of noise control to shock containing jets is a relatively new area

5

Practical Nozzle Geometry• Modern high-performance aircraft have variable geometry nozzles to adapt to different operating conditions

• The “practical nozzle” in the title refers to these

• They differ from traditional C-D nozzles in that they have sharp throats and they are divergent all the way to the exit

• There is almost nothing published about this kind of nozzle

6

Cases

Md = 1.65

Md = 1.50

Md = 1.30

Md = 1.56

Baseline nozzle

Md = 1.5

Chevron capShroud

Md = 1.56

• Practical nozzles simplified to conic C-D

• Chevrons and blowing applied

Md = 1.50

7

Outline




8

Three components of Jet Noise• (Meyer, 1908, Pack, 1950, Lighthill, 1952 & 1954, Ffowcs-Williams, 1963, Lilley, 1974, Crow & Champagne, 1971, Brown & Roshko, 1974, Tam, Golebiowski and Seiner, 1996, Tam, Viswanathan, Ahuja and Panda, 1998, Crow & Champagne, 1971, Brown & Roshko,

1974, Michalke, 1965, Zaman and Hussain , 1984, Yule,1978, Lepicovsky, Ahuja, Brown & Burrin, 1987, Norum & Seiner , 1982, Powell, 1953, Yu & Seiner, 1983, Norum, 1983, Yu & Seiner, 1983, Harper-Bourne & Fisher, 1974, Pao & Salas, 1981, & Seiner, 1983,

Seiner & Yu, 1984, Tam & Tanna, 1982, Tam, Seiner and Yu, 1986, Norum and Shearin, 1986, Bechert, 1975, Jubelin, 1980, Seiner & Norum, 1979, Long and Martens, 2009, Martens and Spyropoulos, 2010, PSU)

• Mixing noise (fine scale and large scale) are common to subsonic and supersonic jets. (peak source location at end of potential

core, broad band)

• Broad-Band Shock-Associated noise (BBSN) arises from interaction between large-scale structures and the shocks in the jet.

(Peak frequency is a function of observer angle, peak source location near later shock cells)

• Screech is a feed-back loop between upstream running BBSN and the large scale structures it induces at nozzle exit (narrow peak,

multiple apparent source locations at shock reflections)

Overexpanded

Perfectly expanded

Underexpanded

9

Before-Chevrons

• Tabs (Bradbury and Khadem,1975, Tanna, 1977, Ahuja, Manes, Massey and Calloway, 1990, Samimy,

Zaman, Reeder, 1993)

• Corrugate jet cross section

• Eliminate screech

• Reduce mixing noise

• The mechanism for noise reduction are streamwise vortices

• Lobes → Tabs → Delta Tabs → Chevrons

Figure from Samimy, Zaman and Reader (1993)

Figures from Smith (1989)

Figures from Saiyed, Mikkelsen and Bridges (2003)

10

Chevrons on subsonic jets• Delta tabs and Chevrons (Saiyed, Mikkelsen and Bridges, 2000 and Bridges and Wernet, 2002, Callender, Gutmark, Martens, 2004 and 2008,

Bridges and Brown, 2004, Opalski, Wernet and Bridges, 2005, Alkislar, Krothapalli and Butler, 2007)

• Similar effects and trends at tabs

• Reduced centerline velocities

• Produced radial velocity (inward at tips, outward in valleys)

• Reduced TKE where it had been highest

• Introduce new TKE near the nozzle

• Require some penetration to work

• Low frequency benefit, high frequency penalty

• Effectiveness increases with penetration and shear velocity

• Same trends for hot jets

• Chevron length is relatively unimportant

• Velocity is important, not temperature or Mach number

• Each source location is moved upstream

11

Chevrons on supersonic jets• Rask, Gutmark and Martens (2006, 2007)

commercial separate-flow exhaust nozzle with centerbody (convergent, Md = 1)

Slightly underexpanded jet, Mj = 1.18. With and without M2 (results for M2 = 0 here)

• Shortened shock cells

• BBSN increased, and shifter to higher freq

• Increased OASPL

• Reduced TKE downstream, increased near-nozzle

• Long and Martens (2009)

Faceted C-D nozzle, Md = 1.3, 1.5, 1.65

Far field 1/3rd

octave band, relative amplitudes only

Near field along a single line, no spectral information

• Reduced forward propagating and aft propagating sound

• Increased high freq near exit reduced low freq downstream

12

Chevrons on supersonic jets (full scale)• Martens and Spyropoulos (2010)

Full scale F404 engine test (engines don’t screech)

Far field 1/3rd

octave band, relative amplitudes only

Jet conditions not shown, but all cases overexpanded

• OASPL reduced,

• small impact on forward propagating

• larger on aft propagating

• Length of chevron is important

13

Microjets on subsonic jets• Introduce streamwise vorticity, but can be turned off

• Air microjets have been studied by (Chauvet, Deck and Jacquin, 2007, Alkislar, Krothapalli and Butler, 2007; Arakeri, Krothapalli,

Siddavaram, Alklislar and Louranco, 2003; Laurendeau, Bonnet and Delville, 2006; Aberg, Szasz, Fuchs, Gutmark, 2007, Alklislar with Krothapalli and Butlerr, 2007, Callender, Gutmark

and Martens, 2007, Camussi, Guj,Tomassi and Sisto, 2008, Zaman, 2007, Castelain, T., Sunyach, M., Juve, D., Bera, J.-C., 2006 and 2008, Krothapalli, Greska and Arakeri, 2002)

• Mutual induction drives vortex pairs in, out (switched)

• Sometimes reduce mixing and lengthen potential core

• Sometimes reduce sometimes increase peak TKE

• Injection angle has influence like penetration

• Microjet self noise contributes to high frequency penalty

• Too many microjets (too close together) spoils effects

14

Microjets on supersonic jets• Krothapalli, Greska and Arakeri (2002)

Convergent, Md = 1.0, Mj = 1.38, hot, 500psi, 1%

• Shock cell length shortened

• OASPL reduced in aft quadrant

• Screech suppressed

• BBSN minimally affected at 90°

• Greska, Krothapalli and Arakeri (2003)

Smooth C-D nozzle, Md = 1.8, Mj = 1.63, 1.8, 1.96, hot, 250 psi

• OASPL reduced

• No screech to eliminate

• Microjet effectiveness reduces if moved downstream

• Henderson and Norum (2007, 2008)

commercial separate-flow exhaust nozzle with centerbody (convergent, Md = 1)

Mj up to 1.16

With and without azimuthal variation, 1.2%

• Mj < 1.06 microjets increased noise

• BBSN reduced

15

Microjets on supersonic jets (full scale)• Greska, Krothapalli, Arakeri (2003), Greska, Krothapalli, Burnside and Horne (2004)

J79 full scale with convergent nozzle, Mj = 1.3, 115-600psi, 0.3-1%

• OASPL reduced

• BBSN reduced

16

Outline




17

Flow Measurement

• Shadowgraph with an Oriel arc lamp and a pair of 12” parabolic mirrors is used with one of the PIV cameras fitted with a telephoto lens

• Centerline pressure was measured by a cone probe, a United Sensor model SDF-15-6-15-600

• LaVision PIV suite• Flow seeded with 1μm

droplets of olive oil• 500 mJ nd:YAG laser formed

into a sheet containing the jet axis

• 2 LaVision 1376x1040 12-bit PIV cameras acquiring simultaneously

• Laser, sheet optics and cameras translate together to 4 streamwise locations for 8 image panes

18

Acoustic MeasurementEX

HA

UST

WA

LL

150°

ARRAY OF FAR-FIELD MICS

NEAR FIELD MIC RAKE:

SOURCE LOCATION

• Adapted from our coaxial flow nozzle model.• 24x25 anechoic chamber good to 500Hz• T0 at Station 0 is uncontrolled, but is around room temperature• 8 B&K ¼” free-field mics from ψ=35° to 150° measured from

upstream• The arc is 47 exit diameters from the nozzle exit• Sampled at 200KHz, good data to 80kHz

35°

UC ACOUSTIC NOZZLE RIG

19

Uncertainty Estimation• Jet velocity is held to within 4.5 m/s (95%) or 1% of velocity so 8% of

Prms or 0.7 dB• Same day acoustic repeatability is 0.6 dB (95%). Agreement with

other facilities is good• PIV seed is around 0.7 μm diameter Stoke’s number ranges from 0.01

to 0.56. Ut/g = 3.0 x 10-4s so a 1000g acceleration will give a terminal velocity 3 orders below Uj

• PIV pressure and shadowgraph compare well with one another and with LES. For x/D < 4 PIV uncertainty is 11 m/s

• PIV quality degrades as one moves downstream.

20

Outline




21

Double Diamond Structure

LES Figure from NRL

• No shock-free condition

• Sharp throat

• Non-parallel exit

• Mj = 1.56 has lip shock

• Later cells unsteady

• Low speed engulfed

• Double diamond previously unreported

22

Influence of Mj

Mj=1.22 Mj=1.36 Mj=1.47 Mj=1.50 Mj=1.56 Mj=1.64 Mj=1.71

• Double diamonds in all cases including design condition

• For overexpanded cases the two diamonds grow closer to one another as Mach disk forms, by Mj = 1.22 they

coalesce by first reflection

• For underexpanded cases the P-M fan from the lip widens until it envelops the throat wave entirely

23

•Prandtl-Pack equation predicts Ls/Dj only a function of Mj, but it reduces with Md also

•Ls for conic C-D nozzles are in line with traditional nozzles

Shock Cell length

24

Increasing Md

Far-field Acoustics

•There is a reduction in screech and a mode switch near Mj = Md

•There is no reduction in BBSN however so shocks must be present.

Md = 1.50 , Mj = 1.50

ψ = 35°

Md = 1.5

ψ = 35°

Md = 1.3

ψ = 35°

Md = 1.65

25

Shock Noise Peak Frequencies

• The frequencies for conical C-D nozzles are indistinguishable from those for traditional C-D nozzles.

• The dependence of frequencies on Md is likely due to the dependence on Ls

• Tam’s equations under-predict, but do better if experimental values for Ls are used in place of Prandtl-Pack

BBSN at 90°Screech

26

Outline




27

Flow Structure• Md = 1.50, Mj = 1.56

• Turbulence from first

• Enhanced spreading

• Diagonal lines in shadowgraph not

in PIV so they’re on surface

28

Influence of Mj

Mj=1.22 Mj=1.36 Mj=1.47 Mj=1.50 Mj=1.56 Mj=1.64 Mj=1.71

• Outer angle changes with Mj, chevron angle does not, effective penetration changes

• Smearing due to shock cell unsteadiness is greater for chevrons for greater Mj

• Vortex shed closer to root and merges earlier for increased Mj (nil for 1.22)

• The “extra” diagonal lines become stronger with increasing Mj by 1.71 they dominate image

29

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a

c

b

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e

f

•Gross changes in shear layer

•Changes in wave angles in shock cells

•Increased TKE near the nozzle

•Axisymmetric by x/De = 4

x/De = 0.5

x/De = 0.5

Tip

Val

Md = Mj = 1.56

x/De

1.0

x/De

2.0

x/De

4.0

30

•Lip wave is shortened by chevrons (c, d, e)

•Throat wave unchanged even after

reflection (f)

•There is no significant difference in the

shock structure between tip and valley

planes

•Lip Shock at (c) strengthened 5% in tip

plane, weakened 4% in valley plane

r/De = 0.0550500

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31

Far-field mixing noise

•For Mj = 1.22 effect is nil. Benefit increases with Mj and effective penetration

•Chevrons kill screech (as do tabs) by breaking symmetry

•BBSN substantially reduced for underexpanded cases (2.3 to 9.1 dB at 90°)

•Peak frequencies shifted higher due to reduction in sonic diameter

•Mixing noise reduction increases with Mj and effective penetration

•Peak reductions of 3.2 to 5.0 dB in mixing noise at 150°

•At forward and side angles reduction occurs below screech frequency

•High frequencies are the only region where we see consistent increases in far-field sound with chevrons

ψ = 35° ψ = 90° ψ = 150°

32

Low f Mixing noise(1000 Hz)

Mj=1.36

Mj=1.50

•Mj = 1.36 shows a reduction in mixing

noise

from x/De = 5 to 10•

Mj = 1.47 it moves downstream (6 to

limit)

•By Mj = 1.56 we start to see a lobe of

increased noise

from x/De = 1.75 to 4•

This lobe does not move, but increases in

intensity

33

Mj=1.64

Screech freq

•Baseline measurements show strong

screech signature

•For Mj below 1.50 there is noise

reduction everywhere

•For higher Mj we see an increase

from x/De = 1.75 to 4

34

Broadband shockassociated noise

•Frequencies selected based on 90° Far-

field peaks•

Mj = 1.36 baseline shows a large lobe

centered at x/De = 5.5•

This lobe shifts to higher f with Mj

increase•

Chevron peak is lower in intensity, farther

downstream•

We do see a lobe of noise building •

at x/De = 1.5 to 3

35

HF noise(30,000Hz)

•This frequency does not discriminate any

particular mechanism•

The high frequencies are the only ones to

show consistent noise increase with

chevrons•

The dominant feature is the lobe of noise

near the nozzle.•

This is counterbalanced somewhat by

decreases downstream in most cases

36

Outline




37

Microjets

• Md = 1.50, Mj = 1.56, arrangement after Alklislar, 1.4% mass to microjets• Increased spreading due to Microjets, though not as much as chevrons• Average of 100 images shows shock cells blurry downstream of microjets• Upstream of microjets is clear, so this is due to unsteadiness in cell structure• Like chevrons, numerous diagonal features are induced by the microjets

38

Microjet self noise

• Over most of the frequency range the microjet self noise is 20 dB lower• This is negligible, so no correction is made for microjet self noise

39

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Soun

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evel

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Frequency [Hz]

Soun

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essu

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evel

ψ = 150°

As measured, 60° by 0° Microjets, Mj = 1.56

Influence of microjet tubes

• Presence of external tubes does have a significant influence on base acoustics

• Screech is suppressed and this suppresses broadband amplification• There is little to be done about this, but to be careful in interpreting the

results

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ψ = 35° ψ = 90° ψ = 150°

Lossless, nondimensional, R/Dj = 100 , Mj = 1.56, cold

Microjet Acoustics

• The Microjets do produce a benefit beyond that produced by the flow-off case

• At 35° both BBSN and screech are reduced beyond the no-flow case• The 90° spectrum shows significant reduction which is important to fly-by or

fly-over extrapolation• BBSN is lowered and shifted to higher frequency like with chevrons• Mixing noise shows low frequency benefit and high frequency penalty as

chevrons do

41

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ψ = 35° ψ = 90° ψ = 150°

Lossless, nondimensional, R/Dj = 100 , Mj = 1.56, cold, 1.4%

10-1

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Stj

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Stj

BaselineMicrojets offMicrojets 54 g/s (max)

Microjet OASPL

• Microjets provide around 0.5 dB additional benefit beyond what tubes alone provide

• Compared to the baseline without tubes, Microjets provide almost 5dB in the forward direction, more than 1 dB atnearly all angles

42

40 60 80 100 120 140125

130

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Inlet angle

OA

SPL

[dB

]

BaselineMicrojets offMicrojets 54 g/s (max)

Full Scale, R = 8m, Mj = 1.56, cold, 1.4%

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Microjets Compared to Chevrons

• The chevrons remove screech as the bare tubes do• Microjet BBSN reduction is less than chevrons, especially at the 90º angle• Mixing noise low frequency benefit is less with microjets that it is with

chevrons• Microjets have a greater high-frequency penalty at aft angles than chevrons

• LES suggests that higher mass flows would bring microjet benefits into line with chevrons

43

ψ = 35° ψ = 90° ψ = 150°

Lossless, nondimensional, R/Dj = 100 , Mj = 1.56, cold, 1.4%

10-1

100

101

90

95

100

105

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Stj

SPL/

Stj

BaselineMicrojets offMicrojets 54 g/s (max)Chevrons

Microjet OASPL compared to chevrons

• Chevrons provide 4dB at the forward angle and 2.25 or 2.5 dB at aft angles

• Chevrons beat microjets at every angle except 35º where they are about equal

44

Full Scale, R = 8m, Mj = 1.56, cold, 1.4%

40 60 80 100 120 140125

130

135

140

Inlet angle

OA

SPL

[dB

]

BaselineMicrojets offMicrojets 54 g/s (max)Chevrons

Outline




45

Summary

• Four areas of contribution– Expanded understanding of the function of

practical C-D nozzles and how they differ from traditional C-D nozzles

– Extended study of chevrons to shock-containing jets and shock-associated noise mechanisms

– Extended study of Microjets to shock-containing jets and shock associated noise mechanisms

– Provided high-quality reference data for CFD

46

Practical C-D Nozzles• Practical C-D nozzles of this type produce no shock-free condition at the

exit. This is due to the non-parallel exit flow.• The sharp throat produces a second set of shock diamonds which are of

comparable strength to the lip shock cells near the design condition

• The presence of shocks at or near the design condition causes shock-associated noise to be present even at the design condition, making further study of shock-containing jet noise important for military engines

• Practical C-D nozzles are like traditional C-D nozzles in several respects– The average shock cell length, Ls compares well with other published values for traditional

C-D nozzles, but not so well to the Prandtl-Pack equation.– This leads the BBSN and screech peak frequencies to be in-line with those of traditional

nozzles, but substituting actual values of Ls improve prediction over Prandtl-Pack

47

Chevrons applied to shock-containing jets

• Chevrons applied to supersonic shock-containing jets behave in many ways like chevrons have previously been found to behave with subsonic jets– They introduce streamwise vorticity and produce a lobed or Corrugated jet cross-section– They enhance bulk mixing, spreading the jet– They reduce low frequency mixing noise downstream, but increase High frequency mixing

noise near nozzle

• Increase in Mj produces a more outward flow angle in the undisturbed jet. Since chevrons do not change their angle, the angle between the undisturbed jet and the chevrons changes with Mj leading to an increased effective penetration as Mj increases

• Thickening of the shear layer reduces potential core radius and sonic radius so the shock cells become shorter

48

Chevrons applied to shock-containing jets

• The shock cell structure is not Corrugated, though shock strengths vary circumferentially

• The initial throat waves are not altered by the presence of chevrons in position or strength

• Chevrons kill screech as tabs do, but breaking symmetry

• Chevrons reduce BBSN and shift the peak to higher frequencies.

49

Microjets applied to shock-containing jets

• Microjets applied to supersonic shock-containing jets behave like chevrons in some ways, and like microjets applied to subsonic jets– They produce a lobed or Corrugated jet cross-section– They enhance bulk mixing, spreading the jet– They reduce low frequency mixing noise downstream, but increase High frequency mixing

noise near nozzle

– They reduce BBSN and shift peak frequencies higher

– The tubes themselves suppress screech, but blowing further reduces it

• The particular arrangement and mass flow rate used here performs less well than chevrons, but LES simulations suggest that higher mass flow will match chevron results

50

Validation data for CFD

pp

uU j

Figures from Liu, et. al.

(2009) AIAA Journal

and AIAA-2009-4004

51

Publications• Journal papers:

• “Flow Structure and Acoustics of Supersonic Jets from Conical C-D Nozzles,” Physics of Fluids (in preparation)

• “Acoustic Effect of Chevrons on Jets Exiting Conical C-D Nozzles,” AIAA Journal (in preparation)

• “Experimental and Numerical Investigation of a Supersonic C-D Nozzle,” Burak, M, Eriksson, L., Munday, D., Gutmark, E., Prisell, E., AIAA Journal (submitted).

• “Supersonic Jet Noise Reduction Technologies for Gas Turbine Engines,” Munday, D., Heeb, N., Gutmark, E., Liu, J., Kailasanath, K., Journal of Engineering for Gas Turbines and Power (accepted)

• “Experimental and Numerical Study of Jets from Elliptic Nozzles with Conic Plug,” Munday, D., Mihaescu, M., Gutmark, E., AIAA Journal (revised, under review)

• “Large-Eddy Simulations of a Supersonic Jet and Its Near-Field Acoustic Properties,” Liu, J., Kailasanath, K., Ramamurti, R., Munday, D., Gutmark, E., Lohner, R., AIAA Journal, Vol. 47, 2009, pp. 1849-1864.

• Conference papers:

• “Fluidic Injection for Noise Reduction of a Supersonic Jet from a practical C-D nozzle,” AIAA/CEAS Aeroacoustics Conference, Stockholm, Sweden, 7-9 June 2010, AIAA-2010-4028

• “Comparison of Flow Control Methods Applied to Conical C-D Nozzles,” 16th AIAA/CEAS Aeroacoustics Conference, Stockholm, Sweden, 7-9 June 2010, AIAA-2010-3874.

• “Forward flight effects on the shock structure from a chevron C-D nozzle,” 48th AIAA Aerospace Sciences Meeting, 5 Jan 2010, Orlando FL, AIAA-2010-0473.

• “Flow Structure of Supersonic Jets from Conical C-D Nozzles,” 39th AIAA Fluid Dynamics Conference, 24 June 2009, San Antonio, Texas, AIAA-2009-4005

• “Acoustic Effect of Chevrons on Jets Exiting Conical C-D Nozzles,” 15th AIAA/CEAS Aeroacoustics Conference, 11 May 2009, Miami, FL, AIAA-2009-3128.

• “Supersonic Jet Noise from a Conical C-D nozzle with Forward Flight Effects,” 47th AIAA Aerospace Sciences Meeting, 5 Jan 2009, Orlando FL, AIAA-2009-0287.

• “Flow and Acoustic Radiation from Realistic Tactical Jet C-D Nozzles,” 14th AIAA/CEAS Aeroacoustics Conference, 5 May 2008, Vancouver, British Columbia, Canada, AIAA-2008-2838.

52

Outline




53

Recommendations for future work• Baseline

– Static pressure survey along centerline– Remove screech by tabs or reflector

• Chevrons– Repeat cross-stream stereo PIV optimized for cross-stream components

• Microjets– Near-field survey– Cross-stream stereo PIV optimized for cross-stream components– Try higher pressure– Embed microjets in the nozzle

• All– POD analysis of PIV– Find Large scale structure size and compare

54

• Effie Gutmark• Shaaban Abdallah, Paul Orkwis, Kailas Kailasanath,

James Bridges

• SERDP and FMV• Steve Martens, B. Gustafsson, M. Bilsson• Kailas Kailasanath, Jun-Hui Liu• Lars-Erik Eriksson, Markus Burak

• Russ Dimicco, Jeff Kastner, Mihai Mihaescu• Nick Heeb, Michael Perrino, Dan Cuppoletti• Chris Harris, Seth Harrison, Olaf Rask, Andrew Rejent,

Romain Girousse

Acknowledgements

55

Questions?

56

Publications• Journal papers:

• “Flow Structure and Acoustics of Supersonic Jets from Conical C-D Nozzles,” Physics of Fluids (in preparation)

• “Acoustic Effect of Chevrons on Jets Exiting Conical C-D Nozzles,” AIAA Journal (in preparation)

• “Experimental and Numerical Investigation of a Supersonic C-D Nozzle,” Burak, M, Eriksson, L., Munday, D., Gutmark, E., Prisell, E., AIAA Journal (submitted).

• “Supersonic Jet Noise Reduction Technologies for Gas Turbine Engines,” Munday, D., Heeb, N., Gutmark,

• E., Liu, J., Kailasanath, K., Journal of Engineering for Gas Turbines and Power (accepted)

• “Experimental and Numerical Study of Jets from Elliptic Nozzles with Conic Plug,” Munday, D., Mihaescu, M., Gutmark, E., AIAA Journal (revised, under review)

• “Large-Eddy Simulations of a Supersonic Jet and Its Near-Field Acoustic Properties,” Liu, J., Kailasanath, K., Ramamurti, R., Munday, D., Gutmark, E., Lohner, R., AIAA Journal, Vol. 47, 2009, pp. 1849-1864.

• Conference papers:

• “Proper Orthogonal Decomposition Analysis of Numerically Simulated Supersonic Jet Flow,” AIAA-2010-4605.

• “Supersonic Jet Noise Reduction by Chevrons Enhanced with Fluidic Injection,” AIAA-2010-4847.

• “Fluidic Injection for Noise Reduction of a Supersonic Jet from a practical C-D nozzle,” AIAA-2010-4028

• “Large-Eddy Simulations of a Supersonic Jet with Fluidic Injection for Noise Reduction,” AIAA-2010-4024

• “Comparison of Flow Control Methods Applied to Conical C-D Nozzles,” AIAA-2010-3874.

• “Micro-jet flow control for noise reduction of a supersonic jet from a practical C-D nozzle,” AIAA-2010-3875

• “Near-Field Jet Noise from a Supersonic C-D Chevron Nozzle,” AIAA-2010-3847

• “Forward flight effects on the shock structure from a chevron C-D nozzle,” AIAA-2010-0473.

• “An Application of Commercial Noise Reduction Techniques to Military Aircraft Nozzles,” AIAA-2010-0656.

• “Flow Structure of Supersonic Jets from Conical C-D Nozzles,” AIAA-2009-4005

• “Experimental and Numerical Investigation of a Supersonic C-D Chevron Nozzle,” AIAA-2009-4004.

• “Impact of Mechanical Chevrons on Supersonic Jet Flow and Noise,” ASME-GT2009-59307.

• “Acoustic Effect of Chevrons on Jets Exiting Conical C-D Nozzles,” AIAA-2009-3128.

• “Large-Eddy Simulations of Imperfectly Expanded Jets from a Chevron Nozzle,” AIAA-2009-3192.

• “Experimental and Numerical Investigation of a Supersonic C-D Nozzle,” AIAA-2009-3253.

• “Supersonic Jet Noise from a Conical C-D nozzle with Forward Flight Effects,” AIAA-2009-0287.

• “Large-Eddy Simulation of a Supersonic Jet and Its Near-Field Acoustic Properties :Methodology and Validation,” AIAA-2009-0500.

• “Investigation of Near-Field Acoustic Properties of Imperfectly Expanded Jet Flows Using LES,” AIAA-2009-0015.

• “Large Eddy Simulation for Turbulent Mixing in Elliptic Jets with Round Center-Body,” AIAA-2009-0079.

• “Flow and Acoustic Radiation from Realistic Tactical Jet C-D Nozzles,” AIAA-2008-2838.

• “Development of a Jet from an Elliptic Nozzle with Round Centerbody,” AIAA-2008-0760.

• “Jet Aircraft Propulsion Noise Reduction Research at University of Cincinnati,”, AIAA-2007-5631

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Documents

Flow and Acoustics of Jets from Practical Nozzles for High-Performance Military Aircraft