Propagation Characteristics of Short Period Regular Wave over Perforated Reef-type Submerged Breakwater Group

Abstract:

Based on flume experiment and numerical simulation， wave transformation and wave-induced current characteristics over a series of periodic distribution of single row perforated reef-type breakwater group with different disposal spaces were studied under short period regular incident wave condition. Wave surface and wave height of reef-type breakwaters without disposal space were measured in a short period incident wave. Wave height is significantly reduced due to the wave energy dissipation caused by wave shoaling effect， but the wave still maintains a quasi-symmetrical sinusoidal wave and propagates for-ward due to the large submergence on the breakwaters. Further， a non-reflected numerical wave model was developed using smoothed particle hydrodynamic （SPH） method and verified by experimental data， which was served to simulate the regular wave propagation over reef-type breakwaters with disposal spacing ratio of 0.5~3.0. The results show that reflection coefficients of all scenarios are above 0.75， indicating that disposal spacing between reef-type breakwaters has a large impact on wave reflection. Transmission coefficients generally decrease with disposal spacing between reef-type breakwaters increasing. It is noticeable that when the spacing ratio is 2.5， the wave reaches the same frequency as breakwaters， triggering the Bragg resonance reflection effect and resulting in the wave height on breakwater-top rising sharply， which causes almost the strongest wave reflection and transmission， and the largest upwelling zone with strong turbulence on the first seaward breakwater.