A quadratic Reynolds stress development for the turbulent Kolmogorov flow

Abstract

We study the three-dimensional turbulent Kolmogorov flow, i.e., the Navier-Stokes equations forced by a single-low-wave-number sinusoidal force in a periodic domain, by means of direct numerical simulations. This classical model system is a realization of anisotropic and non-homogeneous hydrodynamic turbulence. Boussinesq's eddy viscosity linear relation is checked and found to be approximately valid over half of the system volume. A more general quadratic Reynolds stress development is proposed, and its parameters are estimated at varying the Taylor scale-based Reynolds number in the flow up to the value 200. The case of a forcing with a different shape, here chosen Gaussian, is considered, and the differences with the sinusoidal forcing are emphasized.