THE PERFORMANCE OF FLEXIBLE-MEMBRANE WAVE BARRIERS IN OBLIQUE INCIDENT WAVES

The interaction of oblique incident waves with a tensioned, inextensib le, vertical flexible membrane wave barrier hinged at the sea floor is investigated in the context of two-dimensional linear wave-body inter action theory. First, an idealized system (tensioned vertical screen) is considered and analytic solutions are obtained. Second, a more prac tical system with the membrane tension provided by a buoy is investiga ted by a boundary integral equation method. For each case, both submer ged and surface-piercing systems are considered. A two-domain boundary element program is developed based on a discrete membrane dynamic mod el and simple-source distribution over the entire fluid boundaries. Si nce the boundary condition on the membrane is not known in advance, me mbrane motions and velocity potentials are solved simultaneously. The accuracy and convergence of the developed computer program are checked using the energy-conservation formula. The numerical results are furt her verified through comparison with analytic solutions when the buoy is infinitely small. Using the developed computer program, the perform ance of surface-piercing or submerged buoy/membrane wave barriers is t ested with various membrane, buoy, and mooring characteristics and wav e conditions including oblique wave headings. It is found that the eff iciency of a submerged or surface-piercing buoy/membrane breakwater ca n be enhanced in oblique waves for certain design conditions. From our numerical examples, it can be concluded that the buoy/membrane wave b arrier can function as a very effective breakwater for a variety of in cident wave angles if it is properly designed. (C) 1997 Elsevier Scien ce Ltd.