Computational aeroacoustics algorithms: Non-uniform grids

In this paper we consider the application of high-order, high-bandwidth numerical schemes to problems in aeroa-coustics. In particular we consider the effect of choice of grid geometry on the solutions. In the first section of the paper, examples of the effect of non-uniform grids on the solution for the propagation of an initially Gaussian and a cylindrical acoustic source are presented. Dispersion-Relation-Preseverving algorithms are used with modifications for the grid non-uniformity. In the second part of the paper we consider acoustic scattering of a periodic source by a finite plate and a circular cylinder. Two types of boundary treatment for the solid surface are described. The first is a traditional solid wall boundary condition. The second treatment replaces the solid object with a region of high acoustic impedance. Comparisions are made between the different approaches and their advantages and disadvantages are discussed. Finally, some preliminary results for the acoustic scattering of a Gaussian pulse by a circular cylinder are described. Two different approaches are used. One uses a uniform Cartesian grid the other uses a body-fitted coordinate system. The latter approach is implemented on a massively parallel computer.