A GMRES-BASED PLANE SMOOTHER IN MULTIGRID TO SOLVE 3D ANISOTROPIC FLUID-FLOW PROBLEMS

For a discretization of the 3D steady incompressible Navier-Stokes equ ations a solution method is presented for solving flow problems on str etched grids. The discretization is a vertex-centered finite volume di scretization with a flux splitting approach for the convective terms. Second-order accuracy is obtained with the well-known defect correctio n technique (B. Koren, J. Comput Phys. 87, 25, 1990). The solution met hod used is multigrid, for which a plane smoother is presented for obt aining good convergence in flow domains with severely stretched grids. A matrix is set up in a plane, which is solved iteratively with a pre conditioned GMRES method. Here, a stop criterion for GMRES is tested, which reduces the number of inner iterations compared to an ''exact'' plane solver without affecting the multigrid convergence rates. The pe rformance of the solution method is shown for a Poisson model problem and for 3D incompressible channel flow examples. (C) 1997 Academic Pre ss