Scattering of elastic waves by a resonating fluid‐filled cylindrical cavity

Abstract

Resonant excitation of a fluid‐filled cylindrical cavity in an elastic medium by an incident compressional wave is investigated on the basis of resonance theory of nuclear scattering [G. Breit and E. P. Wigner, Phys. Rev. 49, 519 (1936)]. It is shown that the scattering amplitude consists of a series of narrow resonances superimposed upon, and interfering with, a broad background that corresponds to the scattering from an empty cavity. The resonances may be analyzed in a most enlightening fashion by studying them separately in each partial wave of the normal‐mode series. They are seen to correspond to excitations of the eigenvibrations of the cavity fluid caused by a phase match of “creeping waves,” similar to the “Regge poles” of nuclear physics. This paper is part of a series which investigates the excitation of target resonances in the scattering of acoustic and elastic waves using the theory of nuclear resonances. [H. Uberall was supported by the Office of Naval Research, Code 421.]