PROLATE AND OBLATE SPHEROIDAL ACOUSTIC INFINITE ELEMENTS

In a previous paper, the first author presented a new 3-D time-harmoni c prolate spheroidal acoustic infinite element for modeling acoustic f ields in exterior domains. Here, we present the development of the log ical companion to that element, viz. an oblate spheroidal infinite ele ment. Both elements are based on multipole expansions for the acoustic field in spheroidal coordinates developed by the second author in a s eparate paper, recently submitted for publication. For completeness, a n outline of the proofs of convergence of these expansions is included here. Also, essential equations for the previously published prolate spheroidal infinite element are reproduced here in order that this pap er can stand as an independent explication of the spheroidal family of infinite elements. It is shown that a choice of prolate or oblate sph eroidal infinite elements provides a capability for very efficiently m odeling acoustic fields surrounding structures with a wide variety of practical shapes. (C) 1998 Elsevier Science S.A.