Study Of Water Wave Interaction With Submerged Heaving Plate

As a new form of permeable breakwater,submerged horizontal heaving plate breakwater connects to the seabed through a spring with a certain stiffness,so that it can submerge at a certain position below the water surface and oscillate periodically under the waver force.It has the advantage of low coat,low foundation requirement,strong adaptability to water depth,and won't block the water circulation around the structure.Moving wall boundary problem and large deformation of water surface such as wave breaking and water-air mixing is included in the interaction between plate and waves includes,which requires high accuracy and efficiency of the numerical model.In this paper,numerical simulation of water wave(including regular waves and focused waves)interaction with a heaving plate breakwater was performed,using an in-house CIP(Constrained Interpolation Profile)code.The multiphase flow model is built upon a two-dimensional Cartesian grid adopting a CIP scheme as the flow solver.The free surface between fluid and air is captured by THINC/SW(tangent of hyperbola for interface capturing with slope weighting)method,while the interaction of heaving breakwater and water wave is calculated through an IBM(immersed boundary method)method.A momentum source function is applied as internal wave maker to generate regular waves and focused waves.Firstly,the interactions between the fixed horizontal plate and the regular waves as well as focused wave were simulated to verify the reliability of the model,effect of relative width and depth are considered.It was found that the dissipation ability of fixed horizontal plates to regular and freak waves is limited,especially worse to long waves.Then,the process of regular wave evolved on the heaving horizontal plate was investigated numerically.Considerable attention was paid to nonlinear phenomenon such as vortex shedding and wave deformation.The effect of immersed depth and wave conditions on the velocity field,plate response,reflection coefficient and transmission coefficient were discussed.It was found that heaving plate breakwater has much better wave dissipation ability than the fixed one,and has good applicability to waves in a larger frequency range.By comparing the flow field and vorticity field under different conditions,the main energy dissipation modes of heaving horizontal plate were summarized:1.wave energy reflection in front of the plate;2.water deformation,even wave breaking;3.vortex shedding at both ends of the plate;4.the superposition of transmission wave and radiation wave generated by plate movement.Finally,the wave breaking and vortex shedding of focused wave passing through heaving horizontal plate were analyzed,the curves of wave height and energy along the distance were given.The result shows that freak wave can be weaken by heaving horizontal plate.