For Submission to Physics of Fluids a Recommended Modiication to the Dynamic Two-parameter Mixed Subgrid Scale Model for Large Eddy Simulation of Turbulent Flow

It is well known that the correlation between the Smagorinsky model and the subgrid scale stress is low, while the model based on the scale similarity assumption has considerably higher correlation. However, the scale similarity model by itself does not work well in a shear ow simulation because it seems passive on the mean velocity. Therefore the model is usually used together with the Smagorinsky model. Model coe cients are commonly computed using the two-parameter dynamic procedure. Nevertheless, the dynamic two-parameter mixed model still does not work well and the defect of the scale similarity model is not cured by the dynamic procedure. In this study, we propose a modi cation to the two-parameter dynamic procedure, which removes that defect: the Smagorinsky parameter, CS , is computed exactly the same way as in the dynamic Smagorinsky model, then the other parameter, CL, is computed dynamically as CS is known. This ensures that the mixed model has enough eddy viscosity and gives proper mean velocity pro le. Computational tests are done in the turbulent channel ow and the Reynolds numbers based on the channel half width and wall friction velocity are 395 and 1400. To remove the ambiguity regarding the accuracy of the nite di erence scheme, we use high (up to 12-th) order accurate fully conservative nite di erence schemes in a staggered grid system. 2