Technical Report 2006-003

Intermittent Open Boundaries for Shallow Water Equations

Fredrik Bergholm

February 2006

Abstract:
Shallow water equations are used in oceanography, acoustics and electromagnetics. This report (to be submitted as article) focuses on quickly moving shallow water waves in oceanography (also Coriolis force). In wave propagation modelling, it is very often attractive to split up a numerical model into smaller pieces. For barotropic wave modelling, in oceanography, this is almost a necessity. Wave propagation in a submodel communicates with adjacent region(s) by open boundaries. An open boundary is always a half measure, but there are interesting ways of making the open boundaries "softer" - a kind of half-open boundaries. In this article, we investigate the usefulness of having intermittent open boundaries. They tend to produce less errors, and may be analyzed analytically, also. The basic principle is to have both an open boundary condition and a suitable so-called transition condition.

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