An assessment of two models for the subgrid scale tensor in the rational LES model

LES models seek to approximate the large scales of a flow which are defined by a space average (u,p̄) of the velocity u and the pressure p of the flow. A natural question which arises is: Given reliable data for (u,p̄), how accurate is the approximation of (u,p̄) by the solution computed with a LES model? This paper presents numerical studies of this question at a 2d and 3d mixing layer problem for the rational LES model with two types of models for the subgrid scale tensor: the Smagorinsky model and a model proposed by Iliescu and Layton. Whereas in the 2d mixing layer problem the model by Iliescu and Layton showed better results, the behaviour of both models was similar in the 3d mixing layer problem.