Computing Phase Speeds at Open Boundary

Abstract

In the course of modeling hydrodynamic phenomena in a limited area domain, one must specify open boundary conditions. Various forms of the Sommerfeld radiation condition have been used on the boundary of the domain, in the past, to permit internal disturbances to pass unhindered through the boundary. This article shows that if one tries to compute the phase speed associated with the Sommerfeld condition, inevitable numerical errors in this computation adversely affect the interior solutions. A recursive filter that results in smooth, accurate phase speeds and therefore better interior solutions is proposed and its utility demonstrated.