Subgrid-scale modeling with a variable length scale

Length scale variation in subgrid-scale (SGS) modeling is studied using the results from a two-scale direct-interaction approximation. The length scale variation is generated by the advection of SGS eddies by grid-scale ones. This effect leads to the variation of a characteristic SGS length scale around the filter width in the Smagorinsky model. The present model shows that the usual Smagorinsky constant is not a universal constant in large eddy simulation of various types of turbulence.