Response of Bottom-Mounted Fluid-Filled Membrane in Gravity Waves

Abstract

A linear, 2D numerical model is developed to investigate the hydrodynamic characteristics of a bottom-mounted fluid-filled membrane in normally incident waves. The static shape of the membrane, which is noncircular when the densities of the internal and external fluids are different, is computed by considering the equilibrium of the external loads with the membrane hoop stress. A second-order differential equation governing the membrane deformation 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-element models, which in turn are coupled with the finite-element model of the membrane. Both the kinematic and dynamic boundary conditions are satisfied at the fluid-membrane interface, and the steady-state hydrodynamic problem is solved in the frequency domain. The present model and its results are compared with those in a previous study and the differences discussed. Through a parametric study, the density ratio of the internal and external fluids is shown to be an important parameter influencing the dynamic response of the membrane system.