APPROXIMATE RAY SYNTHESIS OF THE SURFACE FIELDS OF A SUBMERGED ELASTIC CYLINDRICAL-SHELL WITH HEMISPHERICAL ENDCAPS

Combining the available ray acoustic algorithms descriptive of submerg ed cylindrical and spherical shells, this paper formulates the pressur e and velocity distributions on a hemispherically capped cylindrical s hell which is immersed in an acoustic fluid and insonified by an obliq uely incident plane wave. As the first ray acoustic model for a noncan onical (nonseparable) shell geometry of considerable current interest, it neglects wave coupling and diffraction due to curvature discontinu ities at the junctures as well as contributions from the leaky waves e xcited through the endcaps. Nevertheless, by matching the surface wave vectors along the joints, due account is taken of leaky wave propagat ion on, and radiation from, the hemispheres. The total pressure or vel ocity on the cylinder-their ray constituents are related to each other by appropriate impedances-is then synthesized by a modified geometric al acoustics field, as developed recently, and a supersonic membrane w ave field. The latter is contributed by the surface leaky rays success ively traveling to the observer along helical trajectories and great c ircles on the cylinder and hemispheres; such rays are excited through phase matching by a series of incident rays, which are in turn identif ied by reciprocal ray tracing so as to quantify the leaky wave contrib ution. Numerical implementation is also performed here. The results ar e compared with the reference solution generated at the Naval Research Laboratory (NRL) by boundary element/finite element codes.