An ILU Smoother for the Incompressible Navier-Stokes
                       Equations in General Coordinates

                           S. Zeng and P. Wesseling
             Department of Technical Mathematics and Informatics
                        Delft University of Technology
                                  Mekelweg 4
                                2628 CD Delft
                               The Netherlands

                                   Abstract

ILU smoothers are good smoothers for linear multigrid methods.  In this paper,
a new ILU smoother for the incompressible Navier-Stokes equations CILU
(Collective ILU), is designed, based on r-transformations.  Existing ILU
decompositions factorize the matrix with real elements.  In CILU the elements
of the matrix that is factorized are submatrices, corresponding to the set of
physical variable.  A multigrid algorithm using CILU as smoother is
investigated.  Average reduction factors and limiting reduction factors are
measured to explore the performance of the algorithm.  The results show that
CILU is a good smoother.