Noise radiation from moving surfaces

摘要

In the present work, the development of a 3-D boundary element method (BEM) for determining the radiation. the reflexion and the diffraction of the sound field around several independently moving bodies with vibrating and, hence, sound producing surfaces is described. Starting from the differential equation for linear acoustics, the so-called general Kirchhoff formula can be derived. This integral equation is the basis for the numerical approximation by the BEM. For the investigation of the sound field of independently moving bodies, an evaluation in the time domain is inevitable. The singular integrals, which arise in the direct BEM, require a careful evaluation. The numerical effort for the calculation and solution of the arising systems of equations can be reduced considerably by restricting the movement of the sound sources to uniform translation with constant velocity. The stability and accuracy of the method is investigated using some simple examples. A comparison with an analytical solution shows that the application of the presented method is possible even at high subsonic speeds (see. Baaran, Schallfeldanalyse bei sich bewegenden schallerzeugenden Korpern. Braunschweiger Schriften zur Mechanik 38-1999. Mechunik- Zentrum der TU Braunschweig 1999). Here, the performance of the algorithm is demonstrated by the computation of two realistic examples,