Reynolds number effect on the velocity derivative flatness factor

International audienceThis paper investigates the effect of a finite Reynolds number (FRN) on the flatness factor (F) of the velocity derivative in decaying homogeneous isotropic turbulence by applying the eddy damped quasi-normal Markovian (EDQNM) method to calculate all terms in an analytic expression for F (Djenidi et al., Phys. Fluids, vol. 29 (5), 2017b, 051702). These terms and hence F become constant when the Taylor microscale Reynolds number, Re λ exceeds approximately 10 4. For smaller values of Re λ , F, like the skewness −S, increases with Re λ ; this behaviour is in quantitative agreement with experimental and direct numerical simulation data. These results indicate that one must first ensure that Re λ is large enough for the FRN effect to be negligibly small before the hypotheses of Kolmogorov (Dokl

WAVELET REGULARIZATION OF A FOURIER-GALERKIN METHOD FOR SOLVING THE 2D INCOMPRESSIBLE EULER EQUATIONS

International audienceWe employ a Fourier-Galerkin method to solve the 2D incompressible Euler equations, and study several ways to regularize the solution by wavelet filtering at each timestep. Real-valued orthogonal wavelets and complex-valued wavelets are considered, combined with either linear or non-linear filtering. The results are compared with those obtained via classical viscous and hyperviscous regularization methods. Wavelet regularization using complex-valued wavelets performs as well in terms of L2 convergence rate to the reference solution. The compression rate for homogeneous 2D turbulence is around 3 for this method, suggesting that memory and CPU time could be reduced in an adaptive wavelet computation. Our results also suggest L2 convergence to the reference solution without any regularization, in contrast to what is obtained for the 1D Burgers equation

Annual Research Briefs, 1990

The 1990 annual progress reports of the Research Fellows and students of the Center for Turbulent Research (CTR) are included. It is intended primarily as a contractor report to NASA, Ames Research Center. In addition, numerous CTR Manuscript Reports were published last year. The purpose of the CTR Manuscript Series is to expedite the dissemination of research results by the CTR staff. The CTR is devoted to the fundamental study of turbulent flow; its objectives are to produce advances in physical understanding of turbulence, in turbulence modeling and simulation, and in turbulence control

ICASE

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in the areas of (1) applied and numerical mathematics, including numerical analysis and algorithm development; (2) theoretical and computational research in fluid mechanics in selected areas of interest, including acoustics and combustion; (3) experimental research in transition and turbulence and aerodynamics involving Langley facilities and scientists; and (4) computer science