Part-II: A Fractional Subgrid-Scale Model for Turbulent Flows*

Following the fractional framework of scalar turbulence, we propose another new fractional approach to modeling the subgrid-scale stresses in large eddy simulation (LES) of turbulent flows. This approach is motivated by the derivation of filtered Navier-Stokes equations with fractional Laplacian. The subgrid-scale velocities are then obtained from a fractional derivative of the resolved-scale quantities, in which the fractional exponent depend on the Reynolds number and the filter length. To study the characteristics of the new model, we compare the results of LES of isotropic turbulent flows against DNS data and examine the accuracy of the results.