5.6   Test Problems

Table 5.A shows the results from computing the potentials exterior to a square. The results from Table 5.B show similar results for the exterior to a sphere. The noticeably less-accurate results in Table 5.B can be attributed to the crude approximation that is made to the sphere. In Table 5.C, the results of Table 5.B are repeated but the sound pressures are given in terms of decibels and phases. This demonstrates another important way of interpreting the results from the subroutines and also shows that often the numerical error appears far less significant when it is viewed in decibel units.

In the final test problem the important Helmholtz property of the radiation ratio is considered. In Figures 5.1 and 5.2 the computed versus exact radiation ratios for pulsating and oscillating spheres across a wide wavenumber range are given where the Helmholtz field is taken to be axisymmetric. The results show some numerical drift from the exact solution with increasing wavenumber. As a general rule, the accuracy of the BEM solution of Helmholtz problems slowly deteriorates with frequency if the same boundary element mesh is used throughout. It may often be necessary to use finer meshes at higher wavenumbers.

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