Scattering from a ribbed finite cylindrical shell

Scattering from a ribbed finite cylindrical shell is investigated with a theoretical formalism valid for long cylinders. An analytic expression is derived for the scattered pressure and it is shown that the scattered far field can be expressed as the sum of three components associated with specular reflection, scattering from helical waves, and Bloch-Floquet waves. Approximate solutions are proposed to reduce the computation load and resonance scattering is analyzed from the derived formulas leading to a relatively simple equation for the calculation of the Bloch-Floquet dispersion curves. Simple equations are proposed to determine the locations of the Bloch-Floquet waves for weak interactions of the ribs and the surface elastic waves. In the first Brillouin zone, it is found that the maximum level of Bloch-Floquet wave scattering depends only on the length of the cylinder as for the resonant modes of uniform cylindrical shells. Finally the relevancy of the method is examined by comparing numerical results to experimental data available in the published literature. (C) 2001 Acoustical Society of America.