The Study Of Hydrodynamic Performance Of Shallow Submerged Horizontal Twin-plate Breakwater

The wave-dissipating performance and wave forces of horizontal plate breakwater are influenced by many factors. Existing research has revealed that compared with single plate breakwater and multi-plate breakwater, twin-plate breakwater has better wave-dissipating performance, and most of the win-plate breakwaters are designed as shallow submerged type. However, existing research achievement lacks of systematic analysis of the varying pattern of wave forces, especially for the research of deep wave-dissipating mechanism and practical scale optimization.In view of the above questions, this dissertation conducts a series of studies related to the hydrodynamic performance of shallow submerged horizontal twin-plate breakwater through both physical model tests and numerical simulation.As for numerical simulation, a2-D numerical wave flume is developed based on FLUENT software.2-D Reynolds-Averaged Navier-Stokes equation, which considers real viscosity, is used together with the UDF function of Fluent. The wave generation source and wave-dissipating source are added in the continuity equation and momentum equation. The VOF method is used to capture free surface. This numerical model can be used to obtain wave pressure on the horizontal plates, wave particle velocity around the breakwater and waveform at the front and back of the breakwater.As for the physical test, wave pressure on the surface of the plates is measured aiming at providing evidence of the numerical model.Based on the physical tests, multiple influencing parameters around a wide range of scale are tested, and the effect of different influencing parameters on wave forces is studied. Through analyzing wave particle velocity pattern and the distribution of wave pressure, the wave-dissipating mechanism and force mechanism are studied. The main research results are listed as following:1. Relative plate width(B/L) and the relative water depth(d/L) are the most important parameter that influences the wave-dissipating performance of the shallow submerged horizontal twin-plate breakwater, and relative distance of two plates(S/H) has small influence on the transmission coefficient2. As for B/L, the wave-dissipating performance is better not because of the wider of plate. The transmission coefficient fluctuates with the increase of B/L (B/L=0.5～1.5). When relative submerge deep(d1/H)=0.4～1.33, S/H=1.0～1.67, B/L=0.8～0.9, the wave-dissipating performance of twin-plate breakwater is optimaL3. As for d/L, the smaller of the d/L, the better the wave-dissipating performance is. When d1/H=0.4～1.33, B/L=0.284～0.67, d/L<0.2, the transmission coefficient is smaller than0.4; when d/L=0.2-0.3, the transmission coefficient changes between0.4and0.7.4. The total of upper plate is almost the same as that of the twin-plate, and they have the similar change trend with the change of B/L, S/H, d/L. The total force of the down plate is much smaller.5. One of the wave-dissipating mechanism of the twin-plate breakwater can be regarded as the blocking-up of normal progression of the waves. The elliptic motion of wave particle is separated and turned into multilayer complex water movement form. In the water area between the two plates, return flow is the main water movement form and the water particles move horizontally. At the front of and the back of the twin-plate breakwater, strong turbulent fluctuation and vortex motion are the main water movement form. Below the breakwater, water particles also move horizontally.6. The collision between progressing waves and return flow is the main factor that generates impact pressure on the surface of the twin-plate breakwater. The front and back end of the upper surface of the upper plate are more likely to be influenced by impact pressure.