A FAST SOLVER FOR NAVIER-STOKES EQUATIONS IN THE LAMINAR REGIME USINGMORTAR FINITE-ELEMENT AND BOUNDARY-ELEMENT METHODS

A multistep method is used to solve the Navier-Stokes equations, formu lated with vorticity and stream function. Each time step is decomposed into three stages: a convection step using the characteristic-Galerki n method, a diffusion step decomposed into a shift to remove the right -hand side, and a linear homogeneous generalized Stokes problem solved by a boundary element method. A domain decomposition method is implem ented with nonconforming mortar elements. In each subdomain we use a f inite element method with isoparametric or overparametric quadrilatera l elements. The quadrangulations for omega and for psi are not necessa rily the same. The boundary element method computes omega at the bound ary but at high Reynolds number it can be replaced by an asymptotic fo rmula. We present numerical tests for flows around cylinders and wing profiles. Results are compared to other authors' and the validity of t he asymptotic formula is investigated.