FLEXURAL VIBRATION OF CYLINDRICAL-SHELLS PARTIALLY COUPLED WITH EXTERNAL AND INTERNAL FLUIDS

In this paper, the free flexural vibrations of a partially fluid-loade d simply supported circular cylindrical shell are studied; the fluid i s assumed to be inviscid and to present a free-surface parallel to the shell axis. The presence of external and internal fluids are both stu died and the problem for incompressible and compressible fluid are bot h discussed by using the added virtual mass approach. Circumferential dependence of displacement is extended in a Fourier series. The maximu m potential energy of the cylinder is evaluated using a sum of referen ce kinetic energies of the shell vibrating in vacuum; this fact allows the proposed method to be independent from the theory of shells used. Then, the Rayleigh quotient for fluid-shell coupled vibration is form ulated and minimized to obtain the Galerkin equation whose solution gi ves the natural frequencies and mode shapes. Numerical computations ar e performed to obtain the modal characteristics as functions of the le vel of water in contact with the shell in the range of good accuracy o f the theory, that is around the half-wet shell level. Results for bot h a shell partially surrounded and filled with water are obtained and compared.