Flexible Membrane Wave Barrier. II: Floating/Submerged Buoy-Membrane System

The interaction of water waves with a tensioned, inextensible, vertical flexible membrane hinged at the sea floor and attached to a solid cylindrical buoy at its top, was investigated in the context of two-dimensional linear wave-body interaction theory. Both submerged and surface-piercing buoy/membrane wave barriers were considered. A two-domain boundary element program was developed based on a discrete-membrane dynamic model and simple-source distribution over the entire fluid boundaries. Since the boundary condition on the membrane is not known in advance, the membrane motion and velocity potentials were solved simultaneously. The accuracy and convergence of the developed program were checked using the energy-conservation formula. The numerical results were further verified by checking several limiting cases and through comparison with the experiments conducted in a 2D wave tank. Using the developed computer program, the performance of surface-piercing or submerged buoy/membrane wave barriers was tested with varying buoy radius and draft, water depth, membrane length, and mooring-line stiffness. The performance of the three different mooring types was also investigated. From our numerical examples, it can be concluded that the buoy/membrane wave barrier can function as a very effective breakwater if it is properly designed.