Filter size definition in anisotropic subgrid models for large eddy simulation on irregular grids

The definition of the characteristic filter size to be used for subgrid scales models in Large Eddy Simulation using irregular grids, is still an unclosed problem. We investigate some different approaches to the definition of the filter length for anisotropic subgrid scale models and we propose a tensorial formulation based on the inertial ellipsoid of the grid element. The results demonstrate an improvement in the prediction of several key features of the flow when the anisotropicity of the grid is explicitly taken into account with the tensorial filter size.