Numerical Study on the Effect of Gap Diffraction on the Hydrodynamic Performance of A Floating Breakwater

Two-dimensional (2D) flume experiments are useful in investigating the performances of floating breakwaters (FBs), including hydrodynamic performances, motion responses, and mooring forces. Designing a reasonable gap between the flume wall and the FBs is a critical step in 2D flume tests. However, research on the effect of the gap on the accuracy of 2D FB experimental results is scarce. To address this issue, a numerical wave tank is developed using CFD to estimate the wave-FB interaction of a moored dual-cylindrical FB, and the results are compared to experimental data from a previously published work. There is good agreement between them, indicating that the numerical model is sufficiently accurate. The numerical model is then applied to explore the effect of gap diffraction on the performance of FBs in 2D experiments. It was discovered that the nondimensional gap length L_Gap/W_Pool should be smaller than 7.5% to ensure that the relative error of the transmission coefficient is smaller than 3%. The influence of the gap is also related to the entering wave properties, such as the wave height and period.