A mixed-time-scale SGS model with fixed model-parameters for practical LES

A new subgrid-scale (SGS) model for practical large eddy simulation (LES) is proposed. The model is constructed with the concept of mixed (or hybrid) time scale, which makes it possible to use consistent model parameters and to dispense with the distance from the wall. The model performance is tested in plane channel flows, and the results show that this model is able to account for near-wall turbulence without an explicit damping function as in the dynamic Smagorinsky model. The model is also applied to the backward-facing step flow examined by Kasagi and Matsunaga (1995) experimentally. The calculated results show good agreement with experimental data, while the results obtained using the dynamic Smagorinsky model show less accuracy and less computational stability. To confirm the validity of the present model in practical applications, the three-dimensional complex flow around a bluff body (Ahmed, 1984) is also calculated with the model. The agreement between the calculated results and the experimental data is quite satisfactory. These results suggest that the present model is a refined SGS model suited for practical LES to compute flows in a complicated geometry.