Behavior of first guided wave on finite cylindrical shells of various lengths: Experimental investigation

Acoustic backscattering from elastic cylindrical shells of finite lengths, immersed in water, is investigated. These objects, characterized by the rat io of length over diameter (L/2a = 9.76, 4.88, 2.44, a: outer radius), are excited by an obliquely incident plane acoustic wave. In the three cases st udied here, the radii ratio b/a (b: inner radius) is fixed at 0.97. The inv estigated dimensionless frequency range extends over 10 less than or equal tok(1)a less than or equal to 50(k(1) : wave number in water). The first gu ided wave, T-0, is of particular interest here. The influence of the shell' s length on the backscattered pressure is experimentally observed in the ti me-angle and frequency-angle representations. In support of this experiment al study, a Lime-domain representation is used by extending a theoretical m odel that provides a geometrical description of the helical propagation or the surface waves around the shell [Bao, J. Acoust. Sec. Am. 94, 1461-1466 (1993)]. Theoretical results on cylindrical shells considered as infinitely long, with identical characteristics, are compared with both experimental representations. (C) 2001 Acoustical Society of America.