Verification of Reynolds stress parameterizations from simulations

TL;DR

This paper evaluates the accuracy of Reynolds stress parameterizations in turbulence models by comparing simulation results with theoretical predictions, focusing on turbulent timescales and their dependence on Reynolds number.

Contribution

It provides new insights into the validity of closure models for turbulent diffusion and isotropization across different Reynolds numbers through direct numerical simulations.

Findings

Turbulent diffusion timescale converges to a constant at high Reynolds numbers.

Isotropization becomes more significant at higher Reynolds numbers.

Closure models are validated against simulation data for anisotropic and decaying turbulence.

Abstract

We determine the timescales associated with turbulent diffusion and isotropization in closure models using anisotropically forced and freely decaying turbulence simulations and to study the applicability of these models. We compare the results from anisotropically forced three-dimensional numerical simulations with the predictions of the closure models and obtain the turbulent timescales mentioned above as functions of the Reynolds number. In a second set of simulations, turning the forcing off enables us to study the validity of the closures in freely decaying turbulence. Both types of experiments suggest that the timescale of turbulent diffusion converges to a constant value at higher Reynolds numbers. Furthermore, the relative importance of isotropization is found to be about 2.5 times larger at higher Reynolds numbers than in the more viscous regime.