A vortex-based model for the subgrid flux of a passive scalar | Zendy

D. I. Pullin | Zendy

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A vortex-based model for the subgrid flux of a passive scalar

Author(s) -

D. I. Pullin

Publication year - 2000

Publication title -

physics of fluids

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.188

H-Index - 180

eISSN - 1089-7666

pISSN - 1070-6631

DOI - 10.1063/1.1287512

Subject(s) - physics , turbulence , scalar (mathematics) , vortex , reynolds stress , mechanics , large eddy simulation , scalar field , classical mechanics , direct numerical simulation , convection–diffusion equation , reynolds number , geometry , mathematics

A model for the flux of a passive scalar by the subgrid motions in the large-eddy simulation of turbulent flow is proposed within the framework of the stretched-vortex subgrid stress model. The model is based on an analytical solution for the winding of a scalar field by an elemental subgrid vortex. This gives a tensor gradient-diffusion expression for the local flux of the scalar with subgrid turbulent diffusivity which depends upon the subgrid energy, the local cell size, and the vortex orientation in space. The scalar-flux subgrid model is tested by comparison of the results of 323 large-eddy simulation of passive-scalar transport by forced isotropic turbulence in the presence of a mean scalar gradient, with the direct-numerical simulation results of Overholt and Pope [Phys. Fluids 8, 2128 (1996)]. The present large-eddy simulation results predict that at large Taylor–Reynolds numbers, the ratio of the scalar variance to the squared product of the scalar gradient with the dissipation length of the turbulence, is asymptotic to a nearly constant value c[prime]2/(alpha1 Lepsilon)2[approximate]0.36.

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