Forced response of neutrally buoyant inflated viscoelastic cantilevers to ocean waves

The dynamics of the neutrally buoyant inflated viscoelastic cantilevers constituting a submarine detection system is investigated. Thin shell theory is used to account for the stresses arising due to the internal pressure. A significant feature of the analysis is the use of the reduced shell equation which is similar in form to that for a vibrating beam with rotary effects. The forcing function in the form of surface wave excitation consists of a fundamental frequency and its second harmonic. Both the effects of apparent inertia and viscous drag are accounted for. The highly complicated non-linear, coupled equations are analyzed numerically. Use of the reduced form of the shell equations appears to avoid the problems of numerical instability and convergence reported by several investigators. The amount of information generated is rather enormous; however, for conciseness, only a few of the typical data, sufficient to establish trends, are presented. The results suggest that for the case of simple harmonicexcitation, the non-linear hydrodynamic drag introduces no superharmonic components into the response. The analysis provides valuable information concerning the system parameters leading to critical response and hence should prove useful in the design of inflatable structural members.