ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

4pPAb2. Radiation from fluid-loaded smooth elastic shells of arbitrary shape.

Yang par


A ray method is systematically used to derive a relation between radiated acoustic waves and elastic waves traveling over a smooth elastic shell of arbitrary shape. The radiated acoustic field is found to be intimately connected with the geometry of the shell's surface and the elastic wavefronts. This connection leads to an asymptotic expression for the local radiation impedance associated with each surface ray under the condition k[sub f]R>>1, where k[sub f] is the wave number in fluid and R the smallest radius of curvature of the shell. The first term in this formula is actually the result for an infinite flat plat, which is homogeneous and isotropic, while the second term introduces inhomogeneity and anisotropy into the radiation impedance because it explicitly depends on the local curvatures of the shell's surface and the elastic wavefronts. The general result is further simplified for a cylindrical shell with cross sections of arbitrary shape. Comparisons are made between the present asymptotic solution and the exact solution in the two special cases of vibrating circular cylindrical shells and spherical shells. It turns out that the first two terms in the asymptotic expansions of these solutions have exactly the same expression. [Work supported by ONR and NRL.] [sup a)]Under contract to Naval Res. Lab., Washington, DC 20375-5000.