Jin-Meng Ho
SFA, Inc., 1401 McCormick Dr., Landover, MD 20785 and Naval Res. Lab., Washington, DC 20375
Combining the available ray acoustic algorithms descriptive of submerged thin cylindrical and spherical shells, this paper formulates the pressure and velocity distributions on a hemispherically capped cylindrical shell insonified by an obliquely incident acoustic plane wave. As the first ray acoustic model for a noncanonical shell geometry of considerable current interest, it neglects wave coupling and diffraction due to curvature discontinuities at the junctures as well as contributions from the leaky waves excited through the endcaps. This might be justifiable, because the junctions are not sharp edges (i.e., the normals are continuous) and because the cylinder under consideration is very long compared to the radius. By matching the surface wave vector along the joints, however, due account is taken of leaky wave propagation on, and radiation from, the hemispheres. The total pressure or velocity---their ray constituents are related to each other by appropriate impedances---on the cylinder is then synthesized by a modified geometrical acoustics field, as developed recently, and a supersonic membrane wave field that accounts for the leaky surface rays successively reaching the observer along helical trajectories and great circles on the cylinder and hemispheres, respectively. Numerical implementation is also performed here. The results are compared with the reference solution generated at NRL by a boundary element code. [Work supported by ONR.]