Dynamic Structure Models for Scalar Flux and Dissipation in Large Eddy Simulation

A new class of subgrid scale models (dynamic structure models) for large eddy simulation is proposed for subgrid scalar flux and dissipation terms. The structure of the modeled terms is taken from the corresponding Leonard terms by the use of the test filter size equal to the base filter size, and a particular form of the scaling factor is proposed. The models are evaluated using available direct numerical simulation data. The evaluation results compare well with viscosity and similarity models. The dynamic structure models have been found to be robust and to work well under various conditions, including various test-to-base filter size ratios and filter skewnesses. Models for both terms employ the subgrid scalar variance as a part of the scaling factor. It is possible not to model the subgrid variance, but to find it via the evolution equation. A new form of the transport equation for subgrid scalar variance that contains only one unclosed term is presented.