Analysis of mean momentum fluxes in subgrid models of turbulence

Yi Li & Charles Meneveau
Department of Mechanical Engineering & Center for Environmental and Applied Fluid Mechanics
The Johns Hopkins University
Baltimore MD 21218

ABSTRACT: Using a recently proposed model spectrum for weakly sheared turbulence, the mean momentum fluxes caused by subgrid scales are evaluated analytically. Using the result to calibrate the Smagorinsky coefficient, the value obtained is remarkably close to the traditional result obtained from balancing kinetic energy dissipation. For the Gaussian filter, the same conclusion is obtained when the Smagorinsky model is supplemented with the nonlinear model. It is concluded that when in practice the Smagorinsky model does not correctly predict the mean SGS stresses in LES, it must be due to either non-universal effects at large scales, or due to strong shear that violates the model spectrum assumed in the present analysis. Analysis of a two-parameter mixed model shows that the nonlinear term must be weighted more strongly in high shear conditions than in weak shear.

Phys. Fluids (2004), 16. 3483-3486.

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(Reused with permission from Yi Li, Physics of Fluids, 16, 3483 (2004), Copyright 2004, American Institute of Physics.)