The Multigrid-Mask Method for Solution of Incompressible
                           Navier-Stokes Equations

                                Hwar-Ching Ku 
             Johns Hopkins University Applied Physics Laboratory 
                    Johns Hopkins Road, Laurel, MD 20723 

                                     and

                             Aleksander S. Popel 
                 Johns Hopkins University School of Medicine 
                    Department of Biomedical Engineering 
                   720 Rutland Avenue, Baltimore, MD 21205

                                   Abstract

A multigrid-mask method for solution of incompressible Navier-Stokes equations
in primitive variable form has been developed.  The main objective is to apply
this method in conjunction with pseudospectral element method solving flow
past multiple objects.  There are two key steps involved in calculating flow
past multiple objects:  The first step utilizes only Cartesian grid points.
This homogeneous or mask method step permits flow into the interior
rectangular elements contained in an object, but with the restriction that the
velocity for those Cartesian elements within and on the surface of an object
should be small with respect to the object.  This step easily produces an
approximate flow field on Cartesian grid points covering the entire flow
field.  The second or heterogeneous step corrects the approximate flow field
to account for the actual shape of the objects by solving the flow field based
on the local coordinates surrounding each object and adapted to it.  The noise
occurring in data communication between the global (low frequency) coordinates
and the local (high frequency) coordinates is eliminated by the multigrid
method when the Schwarz Alternating Procedure (SAP) is implemented.

Two dimensional test problems will be presented to demonstrate the versatility
of the proposed method.