Response of bottom-mounted fluid-filled membrane in gravity waves

A linear, 2D numerical model is developed to investigate the hydrodynamic c haracteristics of a bottom-mounted fluid-filled membrane in normally incide nt waves. The static shape of the membrane, which is noncircular when the d ensities of the internal and external fluids are different, is computed by considering the equilibrium of the external loads with the membrane hoop st ress. A second-order differential equation governing the membrane deformati on due to dynamic loads is derived from the membrane theory of cylindrical shells and it is solved using the finite-element method. The motions of the internal and external fluids are computed, respectively, by two boundary-e lement models, which in turn are coupled with the finite-element model of t he membrane. Both the kinematic and dynamic boundary conditions are satisfi ed at the fluid-membrane interface, and the steady-state hydrodynamic probl em is solved in the frequency domain. The present model and its results are compared with those in a previous study and the differences discussed. Thr ough a parametric study, the density ratio of the internal and external flu ids is shown to be an important parameter influencing the dynamic response of the membrane system.