Advances in the Prediction of the Statistical Properties of Wall-Pressure Fluctuations under Turbulent Boundary Layers (original) (raw)
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International Journal of Heat and Fluid Flow, 2001
The statistical properties of the¯uctuating wall-pressure ®eld are studied using a numerical database generated by large eddy simulation of incompressible turbulent¯ow in a plane channel Re s 640. Emphasis is given on the study of spectral features in the wavevector space and as a function of frequency, particularly in the region of low wavenumbers that are of major concern in submarine applications. A correction procedure is used to cancel the arti®cial pseudo-acoustic eect due to periodic boundary conditions. The in¯uence of superimposed perturbations on one wall of the channel is considered afterwards in comparison with the non-perturbed case. Ó
Flinovia - Flow Induced Noise and Vibration Issues and Aspects, 2014
The various methods to obtain 1-point and 2-point statistical properties of wall-pressure fluctuations from CFD are described and discussed. If only averaged flow quantities are available through Reynolds Averaged Navier Stokes computations, empirical models or sophisticated statistical modeling have to be used to estimate wall-pressure spectra and spatial correlations. While very useful at design stage, their applicability to complex flows or geometries seems quite limited. Considering the rapid growth of computational power, it seems clear that the main pathway for the near future is to rely on time-dependent flow simulations, typically Large Eddy Simulations, and to estimate the pressure statistics through a posteriori signal processing. It seems also possible, at the moment only for relatively high Mach number flows, to estimate not only the hydrodynamic part but also the tiny acoustic contribution. Examples of computations of this acoustic contribution to wall-pressure are given together with related experiments.
An experimental investigation of wall pressure fluctuations beneath non‐equilibrium turbulent flows
The Journal of the Acoustical Society of America, 1988
S2a SECURITY CLASSIFICATION AUTHORITY 3 ViISTRIBjT ION 'AVAILABILI TY OF REPORT lb DECILASIFIICA!ION/t)OWNGRADING SCHEDULE 4 PEFRFORMING ORGANIZATION REPORT NUMBER(S) 5 MONITORING ORGANIZATION REPORT NUMBER(S) I) iv Id 'I'v rNaa Si ',) I I piressuire fluctuations beneath a non-equilibrium turbulent boundary kIV-;Icrwere stI ildit~ e (I.)e rimen tallv. The ohbjec tive of the iovestLi gat ion was to bet ter lillders t~ll IilIhi' I1 'i5 D whlichI turbulent boundary layer flows-)roduce wall pressure f iui'uat illS. I he, lI1p) reich, Wis to ,studv the statistics of both the wail o~ressure field and ye I uicit',' i i"Idi r)!Ji)II-oqn iiibriu]M turbulent boundacv layer, produced by pass ing a flow ovkiT Ai-tI UNCLASSIFIED %U
Numerical Study of Pressure Fluctuations due to High-Speed Turbulent Boundary Layers
2012
Direct numerical simulations (DNS) are used to examine the pressure fluctuations generated by fully developed turbulence in supersonic turbulent boundary layers with an emphasis on both pressure fluctuations at the wall and the acoustic fluctuations radiated into the freestream. The wall and freestream pressure fields are first analyzed for a zero pressure gradient boundary layer with Mach 2.5 and Reynolds number based on momentum thickness of approximately 2835. The single and multi-point statistics reported include the wall pressure fluctuation intensities, frequency spectra, space-time correlations, and convection velocities. Single and multi-point statistics of surface pressure fluctuations show good agreement with measured data and previously published simulations of turbulent boundary layers under similar flow conditions. Spectral analysis shows that the acoustic fluctuations outside the boundary layer region have much lower energy content within the high-frequency region. The space-time correlations reflect the convective nature of the pressure field both at the wall and in the freestream, which is characterized by the downstream propagation of pressure-carrying eddies. Relative to those at the wall, the pressure-carrying eddies associated with the freestream signal are larger and convect at a significantly lower speed. The preliminary DNS results of a Mach 6 boundary layer show that the pressure rms in the freestream region is significantly higher than that of the lower Mach number case. Nomenclature C p heat capacity at constant pressure, J/(K·kg) C v heat capacity at constant volume, J/(K·kg) H shape factor, H = δ * /θ, dimensionless M Mach number, dimensionless P r Prandtl number, P r = 0.71, dimensionless Re θ Reynolds number based on momentum thickness and freestream viscosity, Re θ ≡ ρ∞u∞θ µ∞ , dimensionless Re δ2 Reynolds number based on momentum thickness and wall viscosity, Re δ2 ≡ ρ∞u∞θ µw , dimensionless Re τ Reynolds number based on shear velocity and wall viscosity, Re τ ≡ ρwuτ δ µw , dimensionless T temperature, K T r recovery temperature, T r = T ∞ (1 + 0.9 * γ−1 2 M 2
Outer-flow effects on turbulent boundary layer wall pressure fluctuations
The Journal of the Acoustical Society of America, 1999
The outer-flow contribution to the pressure fluctuations occurring at the wall beneath a turbulent boundary layer was studied experimentally. A moving wall wind-tunnel facility was developed for the work. A flat test plate was suspended at various heights over the movable tunnel wall such that interacting and noninteracting turbulent boundary layers were developed in the resultant channel. Mean and fluctuating velocity components were measured for cases with and without wall motion. Pressure fluctuations were measured, with pinhole microphones on the surface of the test plate forming the upper-channel boundary, at corresponding test conditions. The data show that the wall-pressure fluctuations are relatively insensitive to the details of the outer flow, even over the range of frequencies dominated by outer-flow turbulence structures.
Wall-Pressure Spectral Model Including the Adverse Pressure Gradient Effects
AIAA Journal, 2012
An empirical model to predict the wall-pressure fluctuations spectra beneath adverse pressure gradient flows is presented. It is based on Goody's model which already incorporates the effect of Reynolds number but is limited to zero-pressure gradient flows. The extension relies on 6 test-cases from 5 experimental or numerical studies covering a large range of Reynolds number, 5.6 × 10 2 < R θ < 1.72 × 10 4 , in both internal (channel) and external (airfoil) flows. A review of the boundary layer parameters characterizing the pressure gradient effects is provided and the more relevant ones are introduced as new variables in the model. The method is then compared to the zero-pressure gradient model it is derived from. The influence of the pressure gradient on the wall-pressure spectrum is discussed. Finally, the method is applied to provide input data of radiated trailing-edge noise model by means of an aeroacoustic analogy, namely Amiet's theory of turbulent boundary layer past a trailing edge. The results are compared to experimental data obtained in open-jet anechoic wind tunnel.
Pressure statistics and their scaling in high-Reynolds-number turbulent boundary layers
2007
Pressure fluctuations are an important ingredient in turbulence, e.g. in the pressure strain terms which redistribute turbulence among the different fluctuating velocity components. The variation of the pressure fluctuations inside a turbulent boundary layer has hitherto been out of reach of experimental determination. The mechanisms of non-local pressure-related coupling between the different regions of the boundary layer have therefore remained poorly understood. One reason for this is the difficulty inherent in measuring the fluctuating pressure. We have developed a new technique to measure pressure fluctuations. In the present study, both mean and fluctuating pressure, wall pressure, and streamwise velocity have been measured simultaneously in turbulent boundary layers up to Reynolds numbers based on the momentum thickness R θ 20 000. Results on mean and fluctuation distributions, spectra, Reynolds number dependence, and correlation functions are reported. Also, an attempt is made to test, for the first time, the existence of Kolmogorov's −7/3 power-law scaling of the pressure spectrum in the limit of high Reynolds numbers in a turbulent boundary layer.
Computation of Wall-Pressure Spectra from Steady Flow Data for Noise Prediction
AIAA journal, 2010
A method is proposed to calculate the trailing-edge broadband noise emitted from an airfoil, based on a steady Reynolds-averaged Navier-Stokes solution of the flowfield. For this purpose, the pressure spectrum on the airfoil surface near the trailing edge is calculated using a statistical model from the Reynolds-averaged Navier-Stokes mean velocity and turbulence data in the airfoil boundary layer. The obtained wall-pressure spectrum is used to compute the radiated sound by means of an aeroacoustic analogy, namely, Amiet's theory of airfoil sound. The statistical model for wall-pressure fluctuations is validated with two test cases from the literature, a boundary layer with an adverse pressure gradient, and a flat plate boundary layer without a pressure gradient. The influence of specific model assumptions is studied, such as the convection velocity of pressure-producing structures and the scale anisotropy of boundary-layer turbulence. Furthermore, the influence of the Reynolds-averaged Navier-Stokes simulation on the calculated spectra is investigated using three different turbulence models. The method is finally applied to the case of a Valeo controlled-diffusion airfoil placed in a jet wind tunnel in the anechoic facility of École Centrale de Lyon. Reynolds-averaged Navier-Stokes solutions for this test case are computed with different turbulence models, the wall-pressure spectrum near the trailing edge is calculated using the statistical model, and the radiated noise is computed with Amiet's theory. All intermediate results of the method are compared with experimental data.
Journal of Fluid Mechanics, 1998
Space–time correlations and frequency spectra of wall-pressure fluctuations, obtained from direct numerical simulation, are examined to reveal the effects of pressure gradient and separation on the characteristics of wall-pressure fluctuations. In the attached boundary layer subjected to adverse pressure gradient, contours of constant two-point spatial correlation of wall-pressure fluctuations are more elongated in the spanwise direction. Convection velocities of wall-pressure fluctuations as a function of spatial and temporal separations are reduced by the adverse pressure gradient. In the separated turbulent boundary layer, wall-pressure fluctuations are reduced inside the separation bubble, and enhanced downstream of the reattachment region where maximum Reynolds stresses occur. Inside the separation bubble, the frequency spectra of wall-pressure fluctuations normalized by the local maximum Reynolds shear stress correlate well compared to those normalized by free-stream dynamic p...