Experimental And Numerical Studies On The Transformation Of Wave Propagation Over Submerged Breakwater

Submerged breakwater is one of the most common nearshore breakwaters, whichis widely used to prevent and weaken offshore waves, protect the coast from erosioncaused by the wave and protect the beach and other structures and facilities that arenear the sea. Wave will become deformed because of the complicated topography ofoffshore, resulting in complicated and changeable of the nearshore wave, which makethe wave simulation more difficult, that induce the numerical simulation ofinteractions between waves and submerged breakwater can’t meet the engineeringstandards. So the accurately numerical simulation, interactions between waves andsubmerged breakwater, has become a research hot topic in the field of coastalengineering. This paper will study by the experiment and numerical simulation inorder to check whether the numerical tank could accurately simulate the interactionsbetween waves and submerged breakwater.The experiment is held in the wave tank of marine engineering lab of Oceanuniversity of China; the physical model is trapezoidal submerged breakwater, thewave include regular wave and random wave, the model of submerged breakwaterinclude slope1:2and slope1:5. The wave gauge record wave high, the ADV checkthe current velocity.In this paper, computational fluid dynamics (CFD) software Flow-3D, based onsolving the continuity equation and the incompressible Navier-Stokes equations ofviscous fluid motion, combined RNGκ-ε turbulence model for free surface trackingusing the VOF method, a two-dimensional numerical wave flume is established, in theuse of existing Outflow boundaries on the basis of flow, combined with a porousmedium and variable step method to the end of the tank.By contrast with the physical model test results analysis, porosity and pore structure optimization variable step size grid step long, and then verify the feasibilityand effectiveness of numerical simulation. Submerged breakwater model has beenrefined and validated in the tank to simulate the propagation of waves over submergedbreakwaters, and comparative analysis of physical experiments and numericalsimulation model, simulation optimization at the same time, to get a better fit with theexperimental results numerical solution to analyze waveforms before and after theevolution of submerged breakwater, indicating that Flow-3D numerical model can bea good wave simulation, numerical simulation study for future waves and submergedbreakwater interactions provide valuable experience.The study found in the use of porous media and arithmetic variable step sizeclipping grid method, pore diameter taking0.3m, when the arithmetic take0.05m,clipping effect is relatively best, further studies have shown that the slope of thesubmerged breakwaters have less effect on the transmission coefficient；when thevelocity changes from-0.1m/s to0.3m/s, the transmission first increased and thendecreased, the maximum point corresponding to the velocity of zero; the transmissioncoefficient increases as relative depth of submergence increase, on the contrary, thetransmission coefficient decreases as the period increase.