Visual Analysis of Limited Area Boundary Conditions

摘要

An open boundary is an artificial boundary that does not correspond to a physical boundary. They are used to truncate the domain of a numerical model. Limited area models, such as a regional area model, contain one or more open boundaries. In this work we numerically simulate acoustic wave interference on a 2-dimensional domain to both qualitatively and quantitatively examine the effects of open boundary conditions on a limited-area solution. The resulting interface pattern is used to visualize the impact the boundary conditions have on the fundamental solution modes of the original equation in an intuitive way. The patterns also lead to a fundamental understanding of the structure, not just the magnitude, of the errors. The interference patterns show wide disparity between commonly used boundary conditions, indicating that the quality of the solutions of limited area models can easily be compromised by open boundary conditions with even small magnitude errors. Radiation boundary conditions retained the essential features of the interference pattern most often. However, for long-time simulations, all solutions degraded far beyond our original expectations. Most of the results are not new: it is the qualitative visual analysis of these errors that is the novel component of this study.