Numerical analysis of near and far fields scattered by two plates with finite thickness

Abstract

The multiple scattering in two dimensions of incident plane waves by finite thickness parallel plates is investigated theoretically. The incident wave fronts are perpendicular to the gap between the plates. A boundary element method is used for the calculations. Three distinct scattering phenomena are observed, depending on the wavenumber. Symmetric directivity patterns are observed at the wavenumbers related to the length of the plate. Deep troughs in the backscattering are observed due to destructive interferences of three kinds of scattered waves: the waves scattered from the leading edges of the plates, the travelling waves emanating from the trailing edges, and the waves reflected from the gap between the plates. Strong backscattering peaks are observed at resonance wavenumbers inside the plates. The effects of geometrical parameters are analyzed: the plate thickness to length ratio, the separation gap distance to length ratio, and the plate tip shape. It is found that there are strong correlations between the strong backscattering pressure and the energy inside the plates at the resonance eigen-wavenumbers. (C) 1996 Academic Press Limited