1. PREDICTION OF SHOCK-CELL STRUCTURE
AND NOISE IN DUAL FLOW NOZZLES
Yahia A. Abdelhamid and Ulrich W. Ganz
The Boeing Company, Seattle, WA, 98124
13th AIAA/CEAS
Aeroacoustics Conference
Rome, Italy, 21 - 23 May 2007

2. Background & Motivation
 Broadband shock-cell noise affects the pressure field incident on aircraft aft cabin
 Additional fuselage sidewall treatment may be required to control interior noise levels
 Powell studied Screech tones in some details
 Harper-Bourne & Fisher developed a simple model for shock associated noise
 Seiner & Norum investigated some features of shock noise generation process
 Tam & Tanna proposed the Mach wave radiation model
 Tam developed a stochastic model theory of broadband shock associated noise
 Lui and Lele studied the interaction between a spatially developing, turbulent shear
layer and an isolated oblique compression wave using direct numerical simulation
 Bhat et al. took detailed flow field and near- and far-field acoustic measurements
with model scale nozzles for a typical dual flow exhaust systems. The test was
conducted at the Boeing Low Speed Aeroacoustic Facility (LSAF)
 One of the surprising findings of this study was that the shock-cell noise of dual flow
jets does not necessarily increase monotonically with power settings

3. Overview
 Objectives
 Test Description
 Flow Field Prediction & Validation
 Turbulent Kinetic Energy
 Potential Core & Supersonic Region
 Shock-Cell Noise
 Concluding Remarks

4. Objectives
 Evaluate the Accuracy of Mean Flow Predictions for
Imperfectly Expanded Supersonic Jets Based on RANS
Computations.
 Use of Measured and Predicted Flow Characteristics in
the Interpretation of the Acoustic Data to Better
Understand Shock-Cell Noise Generation Mechanisms
 Develop a Prediction Tool for Shock Associated Noise

5. Test Description
 Most of the test configurations were
based on model scale nozzles of
potential full scale geometries
 During the test, measurements were
made with an array of far field
microphones outside of the
windtunnel flow, with an inflow
phased array of microphones in the
geometric near field of the jet within
the windtunnel flow and with a
wakerake to measure flow
parameters within the jet plume
 More Details can be found in Bhat et
al., AIAA 2005-2929
Test Point PNPR SNPR TTP o
R TTS o
R MT PTFJ TTFJ
TP1 1.61 2.23 1194 564 0.32 15.80 537
TP2 1.82 2.35 1262 576 0.32 15.87 529
TP3 2.04 2.45 1337 586 0.32 15.86 534
TP4 2.17 2.5 1376 591 0.32 15.85 539
TP5 2.3 2.55 1414 597 0.32 15.84 541
TP6 2.38 2.61 1460 601 0.32 15.83 543
TP7 2.04 2.45 500 500 0.33 15.716 510
TP8 2.45 2.45 500 500 0.33 15.718 510
Array position X (inch) Y (inch)
E .0 22.1
F 27. 22.1
G 54. 22.1
Dtot = total plume diameter,
Key Nozzle Operating Conditions
Phased Array Positions
Jet plume cross section at x = 6.0 and 56.4
inches from primary nozzle exit for TP3
X = 6.0 Inch X = 56.4 Inch

6. Flow Field Prediction & Validation
Portion of the axisymmetric grid
used in the flow field prediction
Mach number and
normalized turbulent
viscosity contours
versus normalized
axial distance from
primary nozzle exit
for TP5

7. Flow Field Prediction & Validation
Radial profiles of normalized total pressure for TP2
X = 6.0 Inch X = 16.0 Inch
X = 34.0 Inch X = 56.4 Inch

8. Flow Field Prediction & Validation
Radial profiles of normalized total temperature for TP3
X = 8.5 Inch X = 36.5 Inch

9. Flow Field Prediction & Validation
Normalized static pressure profiles downstream of the primary nozzle exit at
2 radial positions and for TP3, TP4, TP5, and TP6
TP3 TP5
TP4 TP6

10. Turbulent Kinetic Energy
Radial profiles of normalized turbulence kinetic energy at normalized axial
positions of Dtot, 5 Dtot, 9 Dtot, and 12 Dtot

11. Potential Core
Normalized total pressure profiles downstream of the primary nozzle exit at several
axial positions for TP1, TP3, and TP5 operating points
TP1 TP3 TP5

12. Potential Core
Radial profiles of normalized axial velocity at several axial positions downstream
of primary nozzle for test conditions TP1 through TP6

13. Potential Core & Supersonic Regions
Mach number contours for TP1 through TP6

14. Shock-Cell Noise
Narrowband far field sound pressure spectral maps for TP3, TP4 and TP5
Far field sound pressure spectra for TP3, TP4 and TP5 at 3 different radiation angles
TP3 TP4 TP5

15. Shock-Cell Noise
Axial Distance from Primary Nozzle (inch)
NormalizedStaticPressure
0 5 10 15 20 25 30 35 40 45 50 55
0.9
1
1.1
1.2
1.3
TP5 NPR = 2.30 / 2.55 TT = 1418 / 595
TP4 NPR = 2.17 / 2.50 TT = 1379 / 590
TP3 NPR = 2.04 / 2.45 TT = 1340 / 585
aiaa_05_09a
Measured static pressure profiles as a function of axial distance from the primary nozzle
and at constant radial position (Y=2.5 inch) for TP3, TP4 and TP5
Predicted static pressure profiles as a function of distance from the primary nozzle
at 3 radial positions (Y = 2.5, 3.0 and 3.5 inch) for TP3, TP4 and TP5
TP3 TP4 TP5

16. Shock-Cell Noise
Narrowband far field sound pressure spectral maps for test points TP7, TP8 and TP3
Far field sound pressure spectra for test points TP7, TP8 and TP3 at 3 different
radiation angles

17. Shock-Cell Noise
Near field sound pressure spectral maps and spectra based on measurements with
the In-flow Phased Array at 3 different axial positions for TP5 (Nozzle pressure
ratios 2.30 / 2.55, total temperatures 1418 / 595 deg. R)

18. Shock-Cell Noise
Source maps based on measurements with In-flow Phased Array at 3 axial
positions for test point TP5

19. TP3
TP5
TP6
Measured near field sound pressure spectral maps and predicted lines of peak shock-cell
noise for lowest harmonic of shock-cell structure for test conditions TP3, TP5 and TP6

20. Concluding Remarks
 Meanflow predictions for imperfectly expanded dual flow supersonic jets based on
RANS computations were conducted and validated against measured data and are
in good agreement.
 CFD prediction was able to reproduce both shock cell spacing and strength near the
nozzle over a wide range of operating conditions.
 Meanflow prediction confirmed that the shock-cell static pressure variations do not
monotonically increase with operating conditions.
 Measured noise data indicate that shock-cell noise of dual flow nozzle systems is
composed of a low frequency and a high frequency component.
 The low frequency component is associated with the interaction between the
unsteady flow in the outer shear layer with the shock-cell structure.
 The high frequency component is due to the interaction between the shock-cell
structure and the unsteady disturbances of the inner shear layer, the interface
between the high velocity, high temperature of the primary flow and the secondary
flow.
 The low frequency component propagates primarily upstream, whereas the high
frequency component primarily radiates downstream.
 In dual flow jets, the dominant shock-cell noise generation occurs well downstream
of the nozzles. The very intense shock-cell structure along the nozzle geometry
does not seem to contribute significantly to shock-cell noise.