Adapting moment closure for large-eddy simulation of variable density turbulence

Abstract

A new large-eddy simulation (LES) approach is developed for variable density turbulence using moment closure techniques. Even for constant density flows, most current LES models use algebraic closures. The current work introduces two ideas to develop a more advanced closure model. Firstly, moment equations of the type used in higher order Reynolds-averaged Navier–Stokes closures are used to obtain the necessary turbulent quantities. Secondly, the length scale of the filter is related to the scale of the large structures rather than fixed to the grid. These ideas are then applied to the compressible Navier–Stokes equations for two fluids. Preliminary results indicate that the model can be run at quite low resolution compared to conventional LES models without significantly degrading the results. Also, when running in two dimensions the new model is able to capture most of the dissipation that is incorrectly predicted by conventional two-dimensional simulations.