Peculiarities of acoustic beam reflection from a fluid‐solid interface.

Abstract

Mack Breazeale and his colleagues published several papers on experimental study of non‐specular reflection of ultrasonic beam from a fluid‐solid interface [Breazeale et al., J. Acoust. Soc. Am. 56, 866 (1974); J. Appl. Phys. 48, 530 (1977)]. To study fairly unusual details of the reflected beam structure, Schlieren visualization was employed, which clearly confirmed theoretical predictions. The present talk was motivated by this elegant approach of Breazeale. One of the goals was to improve reflected beam imaging by using pulsed Schlieren technique. The second goal was to observe a growing interface wave. It is known that the secular equation for acoustic waves at fluid‐solid interfaces yields the common leaky wave and its complement. This complementary wave grows instead of decays with propagation and is time‐reversed compared to the leaky wave. Ultrasonic pulses and their reflections were visualized using Schlieren imaging and stroboscopic flashing of a semiconductor laser. The source was a broadband (0.5–3 MHz) single element plane transducer. Reflectors were aluminum blocks with fine angular adjustments in an optically transparent water tank. The wave reflection and transmission were also studied numerically using finite differences. [Work was supported by RFBR, NIH, and NSBRI grants.]