IMPLICIT METHOD FOR THE COMPUTATION OF UNSTEADY FLOWS ON UNSTRUCTUREDGRIDS

An implicit method for the computation of unsteady Rows on unstructure d grids is presented. Following a finite difference approximation for the time derivative, the resulting nonlinear system of equations is so lved at each time step by using an agglomeration multigrid procedure. The method allows for arbitrarily large time steps and is efficient in terms of computational effort and storage. Inviscid and viscous unste ady flows are computed to validate the procedure. The issue of the mas s matrix which arises with vertex-centered finite volume schemes is ad dressed. The present formulation allows the mass matrix to be inverted indirectly. A mesh point movement and reconnection procedure is descr ibed that allows the grids to evolve with the motion of bodies. As an example of flow over bodies in relative motion, flow over a multi-elem ent airfoil system undergoing deployment is computed. (C) 1996 Academi c Press, Inc.