Simple conformal methods for finite-difference time-domain modeling of pressure-release surfaces

The finite-difference time-domain (FDTD) method provides a simple and accur ate means of simulating a wide range of acoustic wave propagation problems. Unfortunately, the method has a voracious appetite for computational resou rces. For example, to accurately model scattering from a continuously varyi ng pressure-release boundary, an FDTD grid is typically required that has a much finer discretization than is necessary to model propagation in a homo geneous space. Such a fine discretization can become prohibitive when consi dering large-scale problems. Two simple conformal techniques are presented for acoustic FDTD simulations of problems involving pressure-release bounda ries. These techniques, which rely upon splitting velocity cells adjacent t o the pressure-release boundary, significantly improve the accuracy of the results over those of the standard "staircase" representation of the bounda ry. These methods permit the use of a coarser FDTD grid than would otherwis e be practical and yet add negligible computational cost. The improved accu racy of these split-cell techniques is shown for both a spherical scatterer and a spherical resonator. (C) 1998 Acoustical Society of America. [S0001- 4966(98)03912-5].