The Scattering of Underwater Plane Ultrasonic Waves by Liquid Cylindrical Obstacles

Abstract

An experimental investigation of sound scattering from liquid cylindrical obstacles was performed by Tamarkin following on the work of Bauer and others. A series of scattering patterns, confined to the region about the extended axis of the incident beam and on the opposite side of the obstacle from the source, were determined for ten liquids. The special kia values chosen (ki; = 2π/λi, λi = wavelength of the sound in the medium of the obstacle, a = radius of the cylindrical obstacle) lie in the range 26.0<kia<41.0 and are below and above the corresponding value for the water medium surrounding the obstacle. On the assumption of a plane incident wave, a series solution was found for the total scattered wave and numerical calculations were carried out for conditions approximating those of the actual experiments. The results of this theoretical investigation confirm the experimental findings that scattering of an underwater ultrasonic beam, from the special liquid cylindrical obstacles examined, lies in the zone between the geometrical region and the region of Rayleigh scattering. In this zone, diffraction predominates and the diffraction patterns based on theory agree quantitatively quite well with the positions of the experimental maxima and minima. A rather detailed and extended theoretical study of the resonance curve found experimentally was made and the plotted theoretical resonance curve shows a similar oscillating behavior with amplitude decreasing with increasing kia.