Development of SGS Models for the Dynamic Procedure Using Finite Difference Method : 2nd Report Modeling of SGS Scalar Flux

Abstract

Two different subgrid-scale scalar flux models, namely isotropic and anistropic representation, for the dynamic procedure using finite difference method are derived following the procedure proposed in the previous reports. The proposed models have been assessed on plane turbulent channel flow with passive scalar transport at various grid resolutions and are found to show better agreement with DNS results than those of Smagorinsky's model. The isotropic model is improved to be anisotropic representation by considering the effect of GS velocity gradient on the SGS scalar flux and using the results of a priori test obtained by the LES of a finer grid resolution. The anisotropic model mitigates the isotropic one's overestimation of scalar intensity and streamwise scalar flux near the wall. The notable feature of the proposed models is their insensitivity to the discrete form of the test filtering operation applied during the implementation of the dynamic procedure, which clearly indicates the validity of the proposed models for use in the context of finite difference method.