ASA 125th Meeting Ottawa 1993 May

2pUW1. New range-dependent antisymmetric edge waves along immersed curved elastic wedge with variable cross section.

Jacques R. Chamuel

Sonoquest Advanced Ultrason. Res., P.O. Box 153, Wellesley Hills, MA 02181-5339

Transient antisymmetric edge waves (100 kHz--1 MHz) were propagated along the sharp edge of an immersed curved elastic wedge with variable cross section. Two basic geometrical configurations were investigated. The first was based on a truncated oblique solid cylinder (A 10-cm-diam aluminum cylinder obliquely cut at 22.5(degrees)) forming a convex wedge. The second utilized the intersection of an oblique borehole and a flat solid surface to develop a concave wedge. Aluminum and ice models were studied. The experimental results revealed that the velocity, amplitude, and number of existing antisymmetric edge modes continuously changed as the waves propagated along the range-dependent edge. The antisymmetric edge waves remained nearly nondispersive over a wide frequency range. As the apex angle increased, the number of edge modes decreased. The ratio of the flat side particle displacement to the adjacent curved side particle displacement increased rapidly as the edge apex angle varied between 90(degrees) and 135(degrees). Results from free and immersed wedge models were compared. The new findings contribute to the physical understanding of 3-D range-dependent fluid/solid seismoacoustic wave phenomena applicable to underwater acoustics, nondestructive testing, geophysics, acoustoelectronic devices, and propeller noise. [Work supported by ONR.]