A novel method for expressing anisotropy of subgrid-scale components for thermal and scalar fields

•An anisotropic subgrid-scale (SGS) model for thermal field is proposed.•The model is extended from the anisotropy-resolving SGS model for velocity field.•A priori and a posteriori tests have been done for channel flow.•The proposed model can accurately predict the anisotropic SGS heat flux.•The variation of the anisotropy with Prandtl number can also be expressed. Some types of mixed subgrid-scale (SGS) models combining an isotropic eddy-viscosity model and a scale-similarity model can be used to effectively increase the accuracy of large eddy simulation (LES). For example, Abe (2013) recently proposed a stabilized mixed model, which can successfully express the anisotropy of the SGS stress, and remarkably improves the predictive performance for wall turbulence at coarse grid resolutions without sacrificing computational stability. In the present work, this approach is extended for thermal and scalar field modeling to express the anisotropy of SGS heat (scalar) flux. A priori tests using direct numerical simulation data demonstrated that the proposed model can accurately predict the anisotropic SGS heat flux in channel flow and its variation with Prandtl number in the range 0.1–2. Its effectiveness is also confirmed by a posteriori tests under flow conditions corresponding to those in the a priori tests.