A Simple Compact Fourth-Order PoissonSolver on Polar Geometry

We present a simple and efficient compact fourth-order Poisson solver in polar coordinates. This solver relies on the truncated Fourier series expansion, where the differential equations of the Fourier coefficients are solved by the compact fourthorder finite difference scheme. By shifting a grid a half mesh away from the origin and incorporating the symmetry constraint of Fourier coefficients, we can easily handle coordinate singularities without pole conditions. The numerical evidence confirms fourth-order accuracy for the problem on an annulus and third-order accuracy for the problem on a disk. In addition, a simple and comparably accurate approximation for the derivatives of the solution is also presented. c © 2002 Elsevier Science (USA)