A Parameter Study of the Burton-Miller Formulation in the BEM Analysis of Acoustic Resonances in Exterior Configurations

The application of a boundary element technique in combination with a contour integral approach to the numerical analysis of acoustic resonances in exterior configurations is investigated in this paper. Similar to the boundary element analysis of exterior acoustic radiation or scattering problems, spurious eigenfrequencies also turn up in the boundary element solution to exterior acoustic resonance problems. To filter out the spurious eigenfrequencies, the Burton-Miller-type combined formulation is employed to shift them from the real axis to the complex domain. The shifting effect brought by the combined formulation with different types of coupling parameters is investigated. Unlike in acoustic radiation and scattering analyses for which -i/k is suggested as the coupling parameter, it will be shown that the coupling parameter specified as beta .i/k with beta > 0 (the time-dependent term herein is e(-i omega t)) is more desirable in distinguishing the spurious eigenfrequencies in the boundary element analysis of exterior acoustic resonances.