Acoustic scattering by submerged elastic cylindrical shells: Uniform ray asymptotics

In a uniform ray acoustic formulation, the pressure field scattered by a submerged thin elastic cylindrical shell is comprised of a specular reflected wave field, a phase-matched leaky wave field, and a reflected–leaky wave interacting field. They correspond to the contribution from a saddle point, the residue from spectral poles, and the effect due to their proximity in the spectral ray integral generating the reflected field. Using plane wave far-field scattering as an example, this paper presents an improved uniform algorithm that expresses the third component in terms of the first and second, which have been developed earlier, plus a complementary error function. In addition, the creeping wave contribution is also considered. Numerical implementation is carried out, showing extensively the scattered field data, in particular, their dependence on frequency as well as on aspect and azimuthal angles; the ray constituents and interacting fields are identified individually, thereby clarifying the relevant wave processes at various parameter regimes. It is observed that the uniform ray scheme improves considerably over simple ray asymptotics, especially at lower frequencies, and that its prediction agrees very well with the exact solution for ka≥3.