Experimental performance of multi-layered membrane breakwaters

A series of experimental tests are conducted to investigate the performance of a newly proposed multi-layered flexible membrane breakwater under regular and irregular waves in a two-dimensional wave flume. The effect of various parameters, such as edge conditions, spring stiffness of mooring lines, wave height, wave period, breakwater height, submergence depth of the breakwater, membrane porosity and membrane length, on the efficiency of breakwaters is detailly studied and discussed. The performance of the proposed flexible breakwater is estimated by measuring the wave transmission, reflection and dissipation coefficients through a four-point method based on the least squares method with variable weights and the fast Fourier transform technique. Spectral analysis for irregular waves is also carried out to help understand the experimental results. The results show that the overall trend of the transmission and dissipation coefficients is not significantly different between regular and irregular waves. However, in regular waves, the reflection coefficient fluctuates periodically with respect to the wave period, which does not occur in irregular waves. The experimental data presented here can be used to verify and validate analytical models dealing with similar floating breakwaters.