Stochastic backscatter in a subgrid-scale model: Plane shear mixing layer

Abstract

The traditional Smagorinsky subgrid-scale viscosity (CSλ)2S has been supplemented by the addition of stochastic backscatter. The random acceleration is derived from a vector potential Cb‖S δt‖3/2(λ/δt)2g. Here S is the local strain rate, λ is the grid resolution length scale, δt is the time step, and g is a unit random Gaussian. It is found that values CS=0.2 for the Smagorinsky constant and Cb=0.4 for the backscatter constant give a robust calculation of the two-dimensional shear mixing layer with the observed growth rate and with realistic emergence of random coherent eddy structures.