Geometric evolution of the Reynolds stress tensor

TL;DR

This paper presents a geometric evolution equation for the Reynolds stress tensor in turbulent flows, revealing how mean flow geometry influences turbulence dynamics and proposing an approximate model applicable to shear shallow water flows.

Contribution

It introduces a novel geometric framework for the Reynolds stress tensor evolution and derives an approximate turbulence model with a variational formulation.

Findings

Reynolds stress tensor expressed as sum of tensor products governed by a gyroscopic equation

Approximate turbulence model valid when mean flow vorticity is small

Application of the model to shear shallow water flows

Abstract

The dynamics of the Reynolds stress tensor for turbulent flows is described with an evolution equation coupling both geometric effects and turbulent source terms. The effects of the mean flow geometry are shown up when the source terms are neglected: the Reynolds stress tensor is then expressed as the sum of three tensor products of vector fields which are governed by a distorted gyroscopic equation. Along the mean flow trajectories, the fluctuations of velocity are described by differential equations whose coefficients depend only on the mean flow deformation. If the mean flow vorticity is small enough, an approximate turbulence model is derived, and its application to shear shallow water flows is proposed. Moreover, the approximate turbulence model admits a variational formulation which is similar to the one of capillary fluids.