scholarly journals Numerical Study of Wall Pressure Fluctuations for Zero and Non-Zero Pressure Gradient Turbulent Boundary Layers

2016 ◽  
Author(s):  
Nan Hu ◽  
Christina Appel ◽  
Michaela Herr ◽  
Roland Ewert ◽  
Nils Reiche
Keyword(s):  
Pressure Gradient ◽  
Boundary Layers ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Turbulent Boundary Layers ◽  
Wall Pressure ◽  
Wall Pressure Fluctuations

scholarly journals Influence of pressure gradients on wall pressure beneath a turbulent boundary layer

2018 ◽  
Vol 838 ◽  
pp. 715-758 ◽  
Author(s):  
Elie Cohen ◽  
Xavier Gloerfelt
Keyword(s):  
Pressure Gradient ◽  
Boundary Layers ◽  
Stokes Equations ◽  
Scaling Law ◽  
Pressure Fluctuations ◽  
Turbulent Boundary Layers ◽  
Wall Pressure ◽  
Pressure Gradients ◽  
Wall Pressure Fluctuations ◽  
Significant Difference

This study investigates the effects of a pressure gradient on the wall pressure beneath equilibrium turbulent boundary layers. Excitation of the walls of a vehicle by turbulent boundary layers indeed constitutes a major source of interior noise and it is necessary to take into account the presence of a pressure gradient to represent the effect of the curvature of the walls. With this aim, large-eddy simulations of turbulent boundary layers in the presence of both mild adverse and mild favourable pressure gradients are carried out by solving the compressible Navier–Stokes equations. This method provides both the aeroacoustic contribution and the hydrodynamic wall-pressure fluctuations. A critical comparison with existing databases, including recent measurements, is conducted to assess the influence of a free stream pressure gradient. The analyses of wall-pressure spectral densities show an increase in the low-frequency content from adverse to favourable conditions, yielding higher integrated levels of pressure fluctuations scaled by the wall shear stress. This is accompanied by a steeper decay rate in the medium-frequency portion for adverse pressure gradients. No significant difference is found for the mean convection velocity. Frequency–wavenumber spectra including the subconvective region are presented for the first time in the presence of a pressure gradient. A scaling law for the convective ridge is proposed, and the acoustic domain is captured by the simulations. Direct acoustic emissions have similar features in all gradient cases, even if slightly higher levels are noted for boundary layers subjected to an adverse gradient.

Simulation of turbulent boundary layer wall pressure fluctuations via Poisson equation and synthetic turbulence

2017 ◽  
Vol 826 ◽  
pp. 421-454 ◽  
Author(s):  
Nan Hu ◽  
Nils Reiche ◽  
Roland Ewert
Keyword(s):  
Flat Plate ◽  
Boundary Layers ◽  
Poisson Equation ◽  
Pressure Fluctuations ◽  
Turbulent Boundary Layers ◽  
Wall Pressure ◽  
Fluctuating Pressure ◽  
Reynolds Number Flow ◽  
Wall Pressure Fluctuations ◽  
Interaction Term

Flat plate turbulent boundary layers under zero pressure gradient are simulated using synthetic turbulence generated by the fast random particle–mesh method. The stochastic realisation is based on time-averaged turbulence statistics derived from Reynolds-averaged Navier–Stokes simulation of flat plate turbulent boundary layers at Reynolds numbers $\mathit{Re}_{\unicode[STIX]{x1D70F}}=2513$ and $\mathit{Re}_{\unicode[STIX]{x1D70F}}=4357$. To determine fluctuating pressure, a Poisson equation is solved with an unsteady right-hand side source term derived from the synthetic turbulence realisation. The Poisson equation is solved via fast Fourier transform using Hockney’s method. Due to its efficiency, the applied procedure enables us to study, for high Reynolds number flow, the effect of variations of the modelled turbulence characteristics on the resulting wall pressure spectrum. The contributions to wall pressure fluctuations from the mean-shear turbulence interaction term and the turbulence–turbulence interaction term are studied separately. The results show that both contributions have the same order of magnitude. Simulated one-point spectra and two-point cross-correlations of wall pressure fluctuations are analysed in detail. Convective features of the fluctuating pressure field are well determined. Good agreement for the characteristics of the wall pressure fluctuations is found between the present results and databases from other investigators.

Sign in / Sign up

Export Citation Format

Share Document