Research On Hydrodynamic Of Floating Marine Structures With Wave Absorbing Structure

With the continuous consumption of traditional energy and the increasingly serious global environmental pollution,it is urgent to develop clean and sustainable new energy.As a kind of clean energy,ocean energy has attracted wide attention from all countries in the world with the characteristics of wide distribution,large reserves,and no pollution.With the continuous development of ocean resources,the established Marine infrastructure is seriously damaged by the impact of waves,which has gradually become the main factor restricting the development of ocean energy.Therefore,it is of great significance to study the protection of Marine infrastructure by using wave absorbing structure.In this paper,the application characteristics of wave-absorbing structures such as perforated plate on ocean foundation are studied by CFD numerical simulation method.Firstly,based on the N-S equation of incompressible viscous fluid,a two-dimensional numerical wave flume is established,and a dynamic grid model and VOF method are used to track the free surface for numerical wave generation and wave elimination,and then the accuracy of numerical wave generation,the time step independence and the mesh independence are tested in the same time.It is found that as the size of the grid using?h/H_i<0.17,the time step adopts variable time step which the maximum Cr number is less than 0.5(Cr<0.5),can get better simulation result precision.Secondly,a numerical model of single-layer perforated plate was established to study the wave-absorbing and load-reducing effect of single-layer perforated plate.It is found that for the horizontal wave force acting on the single-layer perforated plate,increasing the porosity of the perforated plate can effectively reduce the horizontal wave force.When the maximum wave force reaches the minimum value,the porosity is around 0.2.When the porosity is unchanged,the horizontal wave force decreases with the increase of Kh.Then the hydrodynamic characteristics of offshore-based Marine infrastructure with perforated plates are studied.The simulation results show that the porosity of the perforated plate and the relative distance between perforated plate and the offshore-based Marine infrastructure,have obvious effects on the wave reflection coefficient of the structure and the horizontal wave force on the whole structure.Under different wave steepness,there is an optimal porosity and relative distance to minimize the wave reflection coefficient and wave force.In the simulation range of this paper,when the wave steepness is 0.095,the best porosity is 0.1 and the best relative distance is between 0.2 and 0.3.When the wave steepness is 0.076,the best porosity is 0.2 and the best relative distance is 0.224.Based on the analysis of the vorticity contours at typical moments,it is found that the wave-eliminating and load-reducing efficiency of the perforated plate is related to the number and size of the vorticity vortices.When the number of vorticity vortices is similar,the existence of small vortices will obviously enhance the wave-eliminating characteristics of the perforated plate.Finally,the hydrodynamic characteristics of floating marine structure with perforated plate are studied.It is found that the porosity of the perforated plate and the relative distance between the perforated plate and the floating marine structure have important effects on the wave reflection coefficient,horizontal wave force and vertical wave force acting on the floating marine structure.With certain combination of parameters,the hydrodynamic characteristics of the floating marine structure can be improved obviously.