Effects of molecular diffusion on the subgrid-scale modeling of passive scalars

Christophe Brun (1) , Guillaume Balarac (1) , Carlos B. da Silva (2) , Olivier Métais (1)

1 LEGI - Laboratoire des Écoulements Géophysiques et Industriels [Grenoble]
2 IDMEC - Instituto de Engenharia Mecânica [Lisboa]

The spectral eddy-viscosity and eddy-diffusivity closures derived from the eddy-damped quasinormal Markovian (EDQNM) theory, and one of its physical space counterparts, i.e., the structure function model [Métais and Lesieur, J. Fluid Mech. 239, 157 (1992)], are revisited to account for molecular viscosity and diffusivity effects. The subgrid-scale Schmidt number ?usually set to (Sct=0.6) is analytically derived from the EDQNM theory and shown to be Reynolds number dependent, a property of utmost importance for flows involving scalar transport at moderate Reynolds numbers or during the transition to turbulence. A priori tests in direct numerical simulation of homogeneous isotropic turbulence [da Silva and Pereira, Phys. Fluids 19, 035106 (2007)] and in spatially evolving turbulent plane jets [da Silva and Métais, J. Fluid Mech. 473, 103 (2002)], as well as a posteriori ?large eddy simulation? tests in a round jet are carried out and show that the present viscous structure function model improves the results from the classical approaches and at a comparatively small computational cost.

Domaines: Mécanique des fluides [physics.class-ph]; Physique mathématique [math-ph]

Christophe Brun, Guillaume Balarac, Carlos B. da Silva, Olivier Métais. Effects of molecular diffusion on the subgrid-scale modeling of passive scalars. Physics of Fluids, 2008, 20 (2), pp.025102. ⟨10.1063/1.2844469⟩. ⟨hal-01713682⟩