On the space‐time characteristics of wall‐pressure fluctuations

1990 ◽  
Vol 2 (8) ◽  
pp. 1450-1460 ◽  
Author(s):  
Haecheon Choi ◽  
Parviz Moin
Keyword(s):  
Pressure Fluctuations ◽  
Space Time ◽  
Wall Pressure ◽  
Wall Pressure Fluctuations

The wall pressure signature of transonic shock/boundary layer interaction

2011 ◽  
Vol 671 ◽  
pp. 288-312 ◽  
Author(s):  
MATTEO BERNARDINI ◽  
SERGIO PIROZZOLI ◽  
FRANCESCO GRASSO
Keyword(s):  
Boundary Layer ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Space Time ◽  
Wall Pressure ◽  
Spanwise Direction ◽  
Frequency Spectra ◽  
Wall Pressure Fluctuations ◽  
Time Correlations

The structure of wall pressure fluctuations beneath a turbulent boundary layer interacting with a normal shock wave at Mach number M∞ = 1.3 is studied exploiting a direct numerical simulation database. Upstream of the interaction, in the zero-pressure-gradient region, pressure statistics compare well with canonical low-speed boundary layers in terms of fluctuation intensities, space–time correlations, convection velocities and frequency spectra. Across the interaction zone, the root-mean-square wall pressure fluctuations attain very large values (in excess of 162 dB), with a maximum increase of about 7 dB from the upstream level. The two-point wall pressure correlations become more elongated in the spanwise direction, indicating an increase of the pressure-integral length scales, and the convection velocities (determined from space–time correlations) are reduced. The interaction qualitatively modifies the shape of the frequency spectra, causing enhancement of the low-frequency Fourier modes and inhibition of the higher ones. In the recovery region past the interaction, the pressure spectra collapse very accurately when scaled with either the free-stream dynamic pressure or the maximum Reynolds shear stress, and exhibit distinct power-law regions with exponent −7/3 at intermediate frequencies and −5 at high frequencies. An analysis of the pressure sources in the Lighthill's equation for the instantaneous pressure has been performed to understand their contributions to the wall pressure signature. Upstream of the interaction the sources are mainly located in the proximity of the wall, whereas past the shock, important contributions to low-frequency pressure fluctuations are associated with long-lived eddies developing far from the wall.

Space–time characteristics of a compliant wall in a turbulent channel flow

2014 ◽  
Vol 756 ◽  
pp. 30-53 ◽  
Author(s):  
Euiyoung Kim ◽  
Haecheon Choi
Keyword(s):  
Channel Flow ◽  
Wall Motion ◽  
Pressure Fluctuations ◽  
Turbulent Channel Flow ◽  
Space Time ◽  
Wall Pressure ◽  
Wall Displacement ◽  
Wall Pressure Fluctuations ◽  
Compliant Wall ◽  
Near Wall

AbstractThe space–time characteristics of a compliant wall in a turbulent channel flow are investigated using direct numerical simulation (DNS). The compliant wall is modelled as a homogeneous plane supported by spring-and-damper arrays and is passively driven by wall-pressure fluctuations. The frequency/wavenumber spectra and convection velocities of the wall-pressure fluctuations, wall displacement and wall velocity are obtained from the present simulation. As the spring, damping, and tension coefficients decrease, the wall becomes softer and the wall displacement and velocity fluctuations increase. For a relatively stiff compliant wall (i.e. large spring, damping and streamwise tension coefficients), there are few changes in the skin-friction drag and near-wall turbulence structures. However, when a compliant wall is soft (i.e. small spring, damping and streamwise tension coefficients), the wall moves in the form of a large-amplitude quasi-two-dimensional wave travelling in the downstream direction. This wave is generated by the resonance of the wall property and the near-wall flow is significantly activated by this wall motion. The power spectra of wall variables show distinct peaks near the resonance frequencies. The convection velocities of the wall motion and wall-pressure fluctuations become smaller with a softer wall.

Modeling the Wavevector-Frequency Spectrum of Boundary-Layer Wall Pressure During Transition on a Flat Plate

1990 ◽  
Vol 112 (4) ◽  
pp. 523-534 ◽  
Author(s):  
M. A. Josserand ◽  
G. C. Lauchle
Keyword(s):  
Boundary Layer ◽  
Frequency Spectrum ◽  
Pressure Fluctuations ◽  
Basic Result ◽  
Space Time ◽  
Wall Pressure ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Turbulent Layer ◽  
Wall Pressure Fluctuations

A spectral model for the wall-pressure fluctuations induced on a zero pressure gradient, flat, rigid surface by a transitioning boundary layer at low Mach number is developed in this paper. The central assumption used in this modeling is that the space-time statistics associated with the formation, convection, and interaction of turbulent spots in a naturally occurring boundary-layer transition are independent of the space-time statistics of the wall-pressure fluctuations that are induced by the turbulence in the individual spots. Space-time correlations for the spots were determined experimentally and semi-empirical formulae are developed to predict these correlations. Previously published statistical descriptions of turbulence-induced wall-pressure fluctuations are coupled with the spot statistics to arrive at the model for the wavevector-frequency spectrum of the transition region. The basic result suggests that the wall-pressure wavevector-frequency spectrum of a transitioning boundary layer is approximately that produced by a fully-turbulent layer weighted by the intermittency factor.

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