INVESTIGATION AND MODELLING OF THE WALL PRESSURE FIELD BENEATH A TURBULENT BOUNDARY LAYER AT LOW AND MEDIUM FREQUENCIES

Abstract In the case of a vehicle moving in a fluid, computation of flow-induced panel vibrations, and the resulting sound generated inside the passenger compartment requires a model that describes the statistics of the turbulent wall pressure fluctuations accurately. However, the models currently available in the literature usually rely on simplifying assumptions and necessitate specific measurements in order to, for example, evaluate the evolution of the coherence length with frequency. This paper describes the work done in order to propose a semi-empirical model for the wall pressure field beneath a fully turbulent boundary layer flow. The main goal is to try to avoid the necessity of preliminary experiments to determine the model coefficients, i.e., propose a model for the power spectral density, coherence length, and phase velocity. After a quick literature review, it proves necessary to acquire a set of experimental data with a fine space–time resolution. Fluctuating wall pressure transducers are developed in this perspective, and experiments are performed in an anechoic wind testing facility. The results are then compared with some published data, analyzed to attempt to offer a schematic description of the physical phenomena involved, and to define the pertinent parameters of the flow and properties of the wall pressure field. These observations are then used to propose a new model for the wall pressure field beneath a fully turbulent boundary layer flow.

[1]  P. Leehey,et al.  Low wavenumber wall pressure measurements using a rectangular membrane as a spatial filter , 1977 .

[2]  Lennart Löfdahl,et al.  Small Silicon Pressure Transducers for Space-Time Correlation Measurements in a Flat Plate Boundary Layer , 1996 .

[3]  Influences of Near-Wall and Induced Irrotational Motion in a Turbulent Boundary Layer on Wall Pressure Fluctuations , 1995 .

[4]  H. Schlichting Boundary Layer Theory , 1955 .

[5]  Mario J. Casarella,et al.  Spectral features of wall pressure fluctuations beneath turbulent boundary layers , 1991 .

[6]  Wr Graham,et al.  A comparison of models for the wavenumber-frequency spectrum of turbulent boundary layer pressures (Reprinted from Proceedings of First CEAS/AIAA Aeroacoustics Conference, June, 1995) , 1997 .

[7]  Günter Schewe,et al.  On the structure and resolution of wall-pressure fluctuations associated with turbulent boundary-layer flow , 1983, Journal of Fluid Mechanics.

[8]  N. Curle The influence of solid boundaries upon aerodynamic sound , 1955, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[9]  M. Bull WALL-PRESSURE FLUCTUATIONS BENEATH TURBULENT BOUNDARY LAYERS: SOME REFLECTIONS ON FORTY YEARS OF RESEARCH , 1996 .

[10]  Michael Fisher,et al.  Correlation measurements in a non-frozen pattern of turbulence , 1964, Journal of Fluid Mechanics.

[11]  William K. Blake,et al.  Turbulent boundary-layer wall-pressure fluctuations on smooth and rough walls , 1970, Journal of Fluid Mechanics.

[12]  W. Willmarth,et al.  Measurements of the fluctuating pressure at the wall beneath a thick turbulent boundary layer , 1962, Journal of Fluid Mechanics.

[13]  V. M. Tkachenko,et al.  Models of a field of pseudoacoustic turbulent wall pressures and experimental data , 1991 .

[14]  P. Jameson Measurement of the Low-Wavenumber Component of Turbulent Boundary Layer Pressure Spectral Density , 1975 .

[15]  D. Chase Modeling the wavevector-frequency spectrum of turbulent boundary layer wall pressure , 1980 .

[16]  F. Fahy,et al.  Mechanics of flow-induced sound and vibration , 1989 .

[17]  C. Zwikker,et al.  Sound Absorbing Materials , 1949 .

[18]  Peter Bradshaw,et al.  ‘Inactive’ motion and pressure fluctuations in turbulent boundary layers , 1967, Journal of Fluid Mechanics.

[19]  M. K. Bull,et al.  High frequency wall‐pressure fluctuations in turbulent boundary layers , 1976 .

[20]  G. Corcos Resolution of Pressure in Turbulence , 1963 .

[21]  M. Bull Wall-pressure fluctuations associated with subsonic turbulent boundary layer flow , 1967, Journal of Fluid Mechanics.