 | Jiao J. Aeroacoustic wind tunnel correction based on numerical: Diss. zur … Dr.-Ing. / Deutsches Zentrum für Luft- und Raumfahrt, Institut für Flugfuhrung, Braunschweig. - Köln: DLR, 2017. - IX,135 p. : ill. - Res. also Germ. - Bibliogr.: p. 131-135. - (Forschungsbericht; 2017-22). - ISSN 1434-8454
Шифр: (Pr 1120/2017-22) 02
|
1 Introduction ............................................... 1
1.1 Background ................................................. 1
1.2 Free shear layer effects in the open-jet test section
wind tunnel ................................................ 2
1.3 Literature review .......................................... 4
1.3.1 Studies on the mean flow gradient effect in the
free shear layer .................................... 4
1.3.2 Studies on the turbulence effect in the free shear
layer ............................................... 6
1.4 Objective and the approach ................................. 8
1.5 Outline of the thesis ...................................... 8
2 Amiet's approach .......................................... 11
2.1 Introduction .............................................. 11
2.2 Basic idea and the correction model ....................... 12
2.3 Angle correction .......................................... 14
2.3.1 Total reflection ................................... 15
2.3.2 Zone of silence .................................... 15
2.3.3 Application of the angle correction in the
open-jet wind tunnel ............................... 16
2.4 Amplitude correction ...................................... 17
2.4.1 Application of the amplitude correction in the
open jet wind tunnel ............................... 18
2.5 Summary ................................................... 19
3 Numerical method .......................................... 21
3.1 Introduction .............................................. 21
3.2 PIANO (Perturbation Investigation of Aerodynamic Noise) ... 22
3.2.1 Governing Equations ................................ 22
3.2.2 Numerical algorithm ................................ 23
3.2.3 Boundary conditions ................................ 24
3.2.4 Sound source model ................................. 25
3.3 Reconstruction of the turbulence (FRPM method) ............ 26
3.3.1 Governing equations ................................ 27
3.3.2 Modeling of turbulent velocities (FRPM method) ..... 28
3.4 Acoustic quantities ....................................... 31
4 Numerical Results ......................................... 33
4.1 Sound propagation through analytical shear layers (2D) .... 33
4.1.1 Computational setup ................................ 33
4.1.2 Characteristics of the base flow ................... 35
4.1.3 Sound propagation through constant thickness
shear layers ....................................... 38
4.1.4 Alteration of the sound wave amplitude through
constant thickness shear layers .................... 45
4.1.5 Sound propagation through wind tunnel shear
layers ............................................. 48
4.1.6 Alteration of the sound wave amplitude through
spreading shear layers ............................. 52
4.1.7 Source directivity in constant thickness and wind
tunnel shear flows ................................. 54
4.2 Sound propagation through the curved shear layer (2D) ..... 56
4.2.1 Computational setup ................................ 56
4.2.2 Characteristics of the base flow ................... 57
4.2.3 Centerline models applied in Amiet's approach ...... 59
4.2.4 Sound propagation through curved shear layers ...... 59
4.2.5 Alteration of the sound wave amplitude through
curved shear layers ................................ 61
4.2.6 Sound propagation through the curved shear layer
considering the nozzle rim reflection .............. 63
4.2.7 Alteration of sound wave amplitude through the
curved shear layer as nozzle surface considered .... 64
4.3 Sound propagation through analytical shear layers (3D) .... 66
4.3.1 Computational setup ................................ 67
4.3.2 Sound propagation through the planar and the
realistic wind tunnel shear layers ................. 68
4.3.3 Alteration of the sound wave amplitude through 3D
analytical shear layers ............................ 77
4.4 Sound propagation through turbulent shear layers (2D) ..... 82
4.4.1 Computational setup ................................ 82
4.4.2 Characteristics of the turbulence part in the
free shear layer ................................... 84
4.4.3 Sound propagation through the turbulent shear
layer .............................................. 85
4.4.4 Alteration of the sound wave characteristics
through the turbulent shear layer .................. 88
4.4.5 Role of turbulent pressure fluctuation in the
scattering effects ................................. 96
4.5 Sound propagation through turbulent shear layers (3D) ..... 96
4.5.1 Computational setup ................................ 96
4.5.2 Sound propagation through the turbulent shear
layer ............................................. 100
4.5.3 Alteration of the sound wave characteristics
through the turbulent shear layer ................. 100
5 Summary, conclusions and outlook ......................... 105
5.1 Summary .................................................. 105
5.2 Conclusions .............................................. 106
5.3 Outlook .................................................. 107
A Derivation of Amiet's approach ........................... 109
A.l Refraction angle change .................................. 109
A.2 Refraction amplitude change .............................. 112
В Figures of the numerical results ......................... 115
С Instabilities in the 3D simulation in the turbulent
shear layer .............................................. 123
Nomenclature .................................................. 127
Bibliography .................................................. 131
|
|
