Experimental Study on the Hydrodynamic Performance of a U-Shaped Flexible Membrane Breakwater

Abstract

Abstract A new U-shaped flexible membrane breakwater is proposed, and its hydrodynamic performance of wave attenuation is experimentally studied in a physical wave flume with piston-type wavemaker. The physical breakwater model is consisted of two U-shaped flexible membranes and four slats. The four slats are stuck to the four ends of the two membranes and fixed near the free surface, and the flexible membranes are extended freely down and form the U-shaped inner and outer layers, with the bottom of the outer membrane lying flat on the flume bottom. The effects of the submerged or immerged depths of the four slats are studied; and a single membrane breakwater is compared with the two-membranes breakwater. A series of monochromatic regular waves are generated at a constant water depth and propagate normally to the breakwater models. The wave elevations on both the windward side and leeward side are recorded by the fixed wave probes respectively. The hydrodynamic performances including transmission coefficient, reflection coefficient and energy dissipation coefficient are calculated, and the variations of the three coefficients versus the relative width are presented. The results demonstrate that the two-membranes breakwater is obviously better than the single membrane breakwater; the slats positions have slight influence on the wave attenuation performances. Overall, the U-shaped flexible membrane breakwater shows a high performance of attenuating wave even for the waves with relatively long wavelength by dissipating the wave energy.