A modal-based multiscale method for large eddy simulation

We introduce a modal spectral element method which employs the variational multiscale approach for large eddy simulation. The method is sufficiently general for application to complex flow geometries, but requires relatively few degrees of freedom for a given mesh and polynomial order. We investigate the performance of the method for fully-developed turbulent channel flow. It is shown that large increases in accuracy can be obtained when the basic dynamics of near-wall coherent structures can be represented using the portion of the modal basis which is free of the subgrid-scale model. This implies that in spite of its lack of orthogonality, the modal basis provides sufficient scale separation to exploit the advantages of the variational multiscale approach.