Numerical Simulation Study On Hydrodynamic Characteristics And Coastal Protection Effects Of New Coastal Protection Structures

In recent years,coastal erosion caused by factors such as sea level rise and human activities has always threatened the safety of people's lives and property.With the launch of the national "Blue Bay Remediation Action" and the promulgation and implementation of the" outline of the national planning for development of ocean economy",Chinese marine economy has entered a new era.In the face of increasingly severe coastal erosion and the trend of marine economic development,the research on protective structures in coastal protection measures is extremely urgent and important.Based on the wave dissipation characteristics of traditional breakwaters and artificial reefs and the idea of beach maintenance,this paper proposes a new type of building that takes into account the effect of wave dissipation and beach maintenance.In this paper,based on the N-S equation,the finite difference method is used to discrete the calculation area,the VOF method is used to capture the free surface change,and the GMRES method is used to solve the pressure and velocity,so as to establish the numerical model of two-dimensional hydrodynamic change numerical model.Secondly,the validity and reliability of the model are verified by multiple examples.Finally,on this basis,the hydrodynamic characteristics of the new building and its beach protection effect are explored.The research results of hydrodynamic characteristics with regular wave as incident wave show that the proposed new coastal protection building reduces the reflection coefficient by 49%at most compared with impervious and porous media buildings.The relative position of the building is between 1 and 1.5,and its transmission coefficient is smaller than that of other positions.The turbulent kinetic energy is mainly distributed in the area behind the breakwater and the wave breaking area.The research results of hydrodynamic characteristics and beach protection effect with isolated wave as incident wave show that in the propagation process of isolated wave,there is obvious hydraulic jump phenomenon in the area behind the embankment,and the wave is finally broken in the form of rolled wave.With the increase of wave height and building placement distance,the transmission coefficient decreases.With the increase of water depth,the transmission coefficient increases;The transmission coefficient of the building is larger when the opening of the backwave surface and the wavefront is larger.The research results of beach protection effect show that under the action of solitary waves,the suspended sediment deposits in the area behind the embankment,and the beach morphology presents a transitional type.With the increase of the number of solitary waves,the height and range of the sand dam and the depth and range of the scour pit increase;Compared with no buildings,the maximum height of the sand dam and the depth of the scour pit are reduced by 29.5%and 13.9%under different wave heights and 9.6%and 19.4%under different water depths.When the wave height is between 0.1 m and 0.215 m,the building reduces 30%?40%beach erosion.Through the comprehensive analysis of the data,in the engineering application,this paper recommends that the opening ratio before and after the building is 5:1,and the position is between 1 and 1.5.