Michael J. Utschig Takeru Igusa Jan D. Achenbach
Dept. of Civil Eng., Northwestern Univ., Evanston, IL 60208
An infinitely long cylindrical shell containing internal substructures and submerged in a fluid is excited by a short duration line load. The response of the shell, substructure, and fluid is examined in the frequency and time domains. To gain insight into the response characteristics, two approaches are used. The first is the normal mode approach, where the response is expressed as a Fourier series in the circumferential coordinate [M. C. Junger and D. Feit (1986)]. In the second approach, the shell is unwrapped into a two-dimensional manifold unbounded in both the longitudinal and circumferential coordinates [Pierce and Kil, J. Vib. Acoust. 112, 399--406 (1990)]. The response is expressed as a Fourier transform in the circumferential coordinate. The results of the modal approach are useful in examining resonances between the fluid-loaded shell and the substructures and in interpreting the effects of the substructure connections. The results of the second approach can be visualized as waves propagating around the shell circumference and generating near-field acoustic disturbances. A time sequence of contour plots of the near-field pressure reveals the evanescent and propagating acoustic waves associated with the shell and substructure responses. [Work supported by ONR.]