Reflection of finite amplitude sound beams from pressure release surfaces

Abstract

A recently described numerical procedure for solving Kuznetsov's nonlinear paraxial wave equation [S. I. Aanonsen, M. F. Hamilton, J. Naze Tjotta, and S. Tjotta, 10th ISNA, Kobe (1984)] is used to model finite amplitude sound beams reflected at normal incidence from both finite and infinite pressure release surfaces. The entire wave field is assumed to be progressive, with reflection simulated by multiplication of each harmonic amplitude by an appropriate coefficient. Although reflection from an infinite pressure release surface reduces finite amplitude losses incurred by the fundamental, it is shown that at some distance from the reflector even the harmonics attain higher axial levels than would occur without reflection. Following reflection from a finite surface, all spectral components exhibit a second nearfield structure characterized by the size of the reflector and the frequency of the component. As a result the axial levels of all components are ultimately higher than after reflection from an infin...