Generation of ultrasonic leaky waves at liquid-solid interfaces

Abstract

Recent experimental investigations by M. A. Breazeale, L. Adler, and G. W. Scott [J. Appl. Phys. 48, 530–537 1977)] have verified the theory of Bertoni and Tamir [Appl. Phys. 2, 157–172 (1973)]. Excitation of leaky Rayleigh waves takes place at the liquid-solid interface when a Gaussian ultrasonic beam is incident at or near the Rayleigh angle to the interface. Now we should like to report two additional examples of leaky wave generation: (1) When a thin (less than a wavelength) ceramic layer is added to a metal surface, leaky waves are generated. The velocity and amplitude distribution of these waves will be discussed. (2) For interfaces such as water-Plexiglas no real solution of the leaky Rayleigh velocity exists since the sound velocity in the water is larger than the shear velocity in Plexiglas. By studying the reflection of an incident Gaussian beam from water-Plexiglas interfaces we have observed leaky waves near the longitudinal critical angle. Similar observations were made at water-sediment interfaces. [M. A. Breazeale and L. Bjørnø, Proc. Ultrasonics Int., 1977, pp. 440–444]. [Research supported in part by the Office of Naval Research.]