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Article Dans Une Revue Journal of Turbulence Année : 2017

Prandtl number effects in decaying homogeneous isotropic turbulence with a mean scalar gradient

Résumé

Decaying homogeneous isotropic turbulence with an imposed mean scalar gradient is investigated numerically, thanks to a specific eddy-damped quasi-normal Markovian (EDQNM) closure developed recently for passive scalar mixing in homogeneous anisotropic turbulence [Briard et al., J. Fluid Mech. 799 (2016)] (BGC). The present modelling is compared successfully with recent direct numerical simulations and other models, for both very large and small Prandtl numbers. First, scalings for the cospectrum and scalar variance spectrum in the inertial range are recovered analytically and numerically. Then, at large Reynolds numbers , the decay and growth laws for the scalar variance and mixed velocity-scalar correlations respectively, derived in (BGC), are shown numerically to remain valid when the Prandtl number strongly departs from unity. Afterwards, the normalized correlation ρ_wθ is found to decrease in magnitude at a fixed Reynolds number when Pr either increases or decreases, in agreement with earlier predictions. Finally, the small scales return to isotropy of the scalar second-order moments is found to depend not only on the Reynolds number, but also on the Prandtl number.
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Dates et versions

hal-01498283 , version 1 (31-03-2017)

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Antoine Briard, Thomas Gomez. Prandtl number effects in decaying homogeneous isotropic turbulence with a mean scalar gradient. Journal of Turbulence, 2017, 18 (5), pp.418-442. ⟨10.1080/14685248.2017.1294253⟩. ⟨hal-01498283⟩
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