Natl. Ctr. for Phys. Acoust., Univ. of Mississippi, University, MS 38677
Kenneth E. Gilbert
Penn State Univ., State College, PA 16804
Univ. of Mississippi, University, MS 38677
A two-dimensional numerical grid generating technique is presented for constructing boundary-fitted coordinates for irregular terrain. In the resulting curvilinear coordinate system, the parabolic equation method is used to compute sound propagation over the terrain. With the proposed numerical grid generating scheme, two separate generating systems are used. One is an orthogonal coordinate generating system, and the other is an elliptical generating system. Used separately, the systems give, respectively, either an orthogonal mapping or a ``smooth'' (equal scaling factors) mapping. By using the two generating systems in conjunction with weighting factors from a variational method, one can control the orthogonality and smoothness of the grid. For certain simple cases, a conformal mapping can be generated by carefully choosing the weighting factors. Preliminary results using the method are compared to exact analytic solutions for a simple test case and, in more complicated cases, to numerical solutions computed by a different method. In principle, the extension of the two-dimensional method to three dimensions is straightforward. The extension to three dimensions in practice and the application to propagation problems with realistic three-dimensional terrain will be briefly discussed.