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Journal Title:Physical Review Fluids
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Description:We highlight the differing roles of vorticity and strain in the transport of coarse-grained scalars at length scales larger than ℓ by smaller scale (subscale) turbulence. We use the first term in a multiscale gradient expansion due to Eyink [J. Fluid Mech. 549, 159 (2006)], which exhibits excellent correlation with the exact subscale physics when the partitioning length ℓ is any scale smaller than that of the spectral peak. We show that unlike subscale strain, which acts as an anisotropic diffusion/antidiffusion tensor, subscale vorticity's contribution is solely a conservative advection of coarse-grained quantities by an eddy-induced nondivergent velocity, v∗, that is proportional to the curl of vorticity. Therefore, material (Lagrangian) advection of coarse-grained quantities is accomplished not by the coarse-grained flow velocity, ¯¯¯uℓ, but by the effective velocity, ¯¯¯uℓ+v∗, the physics of which may improve commonly used LES models.
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Source:Phys. Rev. Fluids 7, 104601
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Rights Information:Accepted Manuscript
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Compliance:Submitted
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