Acoustic scattering by a metallic tube with a concentric solid polymer cylinder coupled by a thin water layer. Influence of the thickness of the water layer on the two Scholte–Stoneley waves

The problem of a plane acoustic wave scattered by a layered cylinder submerged in water is considered. This cylinder consists of a tube made of aluminum with a solid Lucite cylinder concentrically fitt inside it. These two components are coupled by a thin layer of water. A particular investigation is made on the influence of the thickness of the water layer on the presence of the bending wave A on the tube and the Scholte–Stoneley wave on the cylinder. The presence of these waves is examined in the function of the varying water layer thickness: two special cases are discussed. First, for a layer thickness greater than the tube thickness, it is shown that both the A wave on the aluminum tube and the Scholte–Stoneley wave on the Lucite cylinder are generated. Second, for a thickness much smaller than the tube thickness, a different wave is generated, which is a combination of both waves. These two cases are experimentally verified in a setup that employs a short pulse method.