Simulation Study On Structural Design And Layout Of Arc-plate Permeable Dike Under Different Tidal Range Scenarios

The plate-type permeable dike has been paid much attention by experts and scholars for its superior wave dissipation ability.Compared with the gravity breakwater,the plate type permeable breakwater has lower engineering cost and is conducive to the free exchange of water inside and outside the port area.It can effectively reduce the flow velocity at the mouth of the ebb and flow tide,and has little impact on the ecological environment.Therefore,it is a new type of breakwater that is environmentally friendly and meets the requirements of ecological civilization construction.Some scholars compared three types of permeable dikes,namely,upper arc plate type,lower arc plate type and flat plate type,and pointed out that the lower arc plate type structure has certain advantages of wave elimination.There is a wave climbing process in the bottom-arc plate permeable dike,which is easy to form a large water tongue,and the collapse of the water tongue can dissipate more energy.Therefore,this paper mainly studies the lower arc plate permeable dike and designs three types of structure.At present,the research on arc plate permeable dike mainly uses the transmission coefficient calculated by the transmission wave height to measure the wave dissipation performance of the structure,and seldom evaluates the wave dissipation effect from the perspective of wave energy flow.The wave energy flow takes three parameters of wave height,water depth and period into consideration,which has some advantages compared with the transmission coefficient which only considers wave height.In this paper,based on the physical model test of arc-plate permeable dike,in addition to analyzing the permeability and reflection coefficients,the wave energy flow in different scenarios will be calculated,and the influencing factors of wave energy flow in the wave-facing and wave-back direction of the permeable dike will be discussed.It is concluded that relative plate width,position parameters,wave height and water entry depth have more significant effects on wave energy flow than plate spacing.Previous studies have made rich achievements in the field of hydrodynamic characteristics of arc-plate permeable dikes.However,there are few studies on the wave-reducing effect of arc-plate permeable dikes with different structural types under different tidal range conditions,and the engineering application of arc-plate permeable dikes resulting in tidal range changes lacks relevant theoretical support.Due to the time consuming and labors of physical model test,numerical method will be used to study the arc-plate permeable dike under different tidal range.In this paper,based on Fluent software,the continuity equation and momentum equation are taken as the fluid governing equations,and C++ is used for custom programming to realize wave generation and wave elimination.The VOF method is used to track the free surface of the fluid,and the numerical model of the interaction between waves and the porous dike is established.In test and verify the reliability of the numerical wave and wave,grid independence,on the basis of the arc plate type void,dike built by physical model test results verified the accuracy of the numerical model,this paper discusses the small,medium and three kinds of tidal range,different structure of the arc plate type void,dike wave,wave energy flow and flow field characteristics,given different tidal range used nearby dam structure and layout proposal: In the case of low tidal range,the single-arc-plate permeable dike slightly lower than the low tidal level can exert better wave dissipation effect,and the recommended value range of the relative water entry depth of the permeable dike is 0.02～0.07.In the case of intermediate tidal range,the double-arc-plate permeable dike with the upper and lower arc-plates located below the low tide level and the high tide level respectively has a better wave dissipation performance.In the case of spring tide difference,at least three layers of arc plate should be arranged from low tide level to high tide level,and the value range of relative water entry depth of the uppermost arc plate of arc plate permeable dike is suggested to be 0.02～0.07.The research results can provide relevant theoretical guidance for the actual engineering construction.