The discrete artificial boundary condition on a polygonal artificial boundary for the exterior problem of Poisson equation by using the direct methodof lines

The numerical simulation for the exterior problem of Poisson equation is co nsidered. We introduced a polygonal artificial boundary Gamma(e) and design ed a discrete artificial boundary condition on it by using the direct metho d of lines. Then the original problem is reduced to a boundary value proble m defined in a bounded computational domain with a polygonal boundary. The finite element approximation of this reduced boundary value problem is cons idered and it is proved that the finite element approximate problem is well posed. Furthermore numerical examples show that the discrete artificial bo undary condition is very effective and more accurate than the Neumann bound ary condition which is often used in engineering literatures. (C) 1999 Else vier Science S.A. All rights reserved.