TIME ANALYSIS OF IMMERSED WAVE-GUIDES USING THE FINITE-ELEMENT METHOD

The propagation of acoustic waves in immersed waveguides has been prev iously studied with the help of the finite element method, using the A TILA code [A. C. Hladky-Hennion et al., J. Sound Vib. 200, 519-530 (19 97)]. But this method, which is a modal analysis, essentially concerns the case of rectilinear, infinite, and uniform waveguides. Thus this paper deals with another way of solving the problem of wave propagatio n along waveguides, with the help of a time analysis using finite elem ents. First, the theoretical formulation is presented for immersed str uctures. Then, Plexiglas and brass wedge guides, of different apex ang les, are considered. When immersed in water, these wedges generate eit her propagating or radiating wedge waves. The finite element results, using a time analysis, are compared to the previous finite element res ults, using a modal analysis and to the experiments, leading to a good agreement. Thus the approach can be easily extended to other waveguid es whatever their cross sections. (C) 1998 Acoustical Society of Ameri ca. [S0001-4966(98)02306-6].