Large eddy simulation of scalar turbulence using a new subgrid eddy diffusivity model

A new subgrid eddy diffusivity model is used for large eddy simulation of scalar turbulence. The new model is based on the modified Yaglom equation, i.e., the dynamical equation for the structure function of resolved-scale scalar fluctuations, by which the scalar transport between resolved grid scale and unresolved subgrid scale can be described exactly. The new model has been applied in the large eddy simulations of scalar transport in both decaying isotropic turbulence and fully developed turbulent channel flow. By the comparison with Smagorinsky model and the dynamical model, it is found that the new model can achieve similar accuracy as the dynamical model, and can reduce the computational cost about 20% in terms of CPU time relative to the dynamical model