Approximate ballooning techniques

The solution of 2D open boundary problems can be obtained using static ballooning techniques [1] by defining both a closed boundary surrounding the model to be analyzed and the directions of expansion of the inner boundary nodes. In certain special cases when the exterior region exhibits geometric symmetry it is possible to use a circular boundary. The paper describes a process in which the coefficients of the exterior region matrix can be easily and economically obtained using a precomputed stored table of values and a simple derived expression. It is also presented an algorithm to compute the coefficients of the full exterior region from the equivalent half space problem, saving then a considerable amount of time.