Large eddy simulation of unsteady rotor-stator interaction in a centrifugal compressor

A proof of concept, LES computation of the flow through a centrifugal compressor is carried out. The large cost of such a computation limits its use to flows such as the jet-wake flow in a centrifugal compressor for which more economical approaches are unsuitable. We solve the 3D, unsteady, compressible Navier-Stokes equations numerically on an unstructured, tetrahedral grid in a time accurate manner using a finite volume formulation. Convective fluxes at the cell interfaces are computed using the fluctuation splitting concept. A Galerkin formulation is used for the viscous terms. A multi-level generalization of the dynamic subgrid stress model is used. The code uses adaptive grids and a multigrid acceleration procedure with a four stage Runge-Kutta smoother. A hierarchical, octree organization of the data is employed with a single tetrahedron division rule. This is shown to allow significant reductions in memory usage. Comparisons with rotating channel experimental, LES and DNS data are carried out. A comparison with the Eckhardt compressor measurements show qualitative agreement in the quasi-steady state case. The unsteady rotor-stator interaction results are preliminary and await a parallel and as yet uncompleted experimental program validation.