An efficient mixed dynamic Smagorinsky/scale-similarity subgrid model

It is well known that scale-similarity models have a high correlation of the subgrid stresses with the true stresses in a priori tests but provide very little subgrid dissipation to be practically useful. On the other hand, eddy-viscosity models such as the dynamic Smagorinsky model predict the subgrid dissipation well but correlate poorly with true subgrid stresses. This has motivated the use of mixed subgrid models that appear to retain the benefits of both models. However, dynamic mixed models typically require two or more levels of test filtering beyond the baseline (often implicit) grid filter, which makes it computationally expensive and cumbersome to implement and has limited their use in production codes. We propose an efficient mixed subgrid model with a single level of test filtering and evaluate its performance through a priori and a posteriori testing of canonical flows including decaying isotropic turbulence and turbulent plane channel flows.