Study On The Interaction Between Two-dimensional Submerged Cylinder And Nonlinear Wave

The free surface effect and the motion of structures near the free surface are the focus and difficulty of hydrodynamic research,and also the issues that need to be considered in the field of ship and ocean engineering.Many operations in ocean engineering need to consider the effects of free surface and waves,such as the motion of offshore platforms and ships in wind and waves,the deployment and recovery of underwater vehicles,robots,and the deep navigation of submarines near the water surface or emergency hovers and missile launches,etc.Therefore,it is necessary to study the motion of ocean structures near the free surface and analyze the influence of wind and waves on the motion of the structures.In this paper,the motion and wave-making of a two-dimensional simple structure near the free surface have been investigated,including the steady motion of the immersed elliptical cylinder in shallow water and the coupled motion of the immersed cylinder with the nonlinear wave.The wave induced by steady motion of immersion cylinder in shallow water and the influence of wave on the motions of submerged cylinder have been analyzed.Ignoring the viscosity and compressibility of the fluid,the velocity potential is used to describe the flow fields.The nonlinear boundary conditions are imposed on the free surface and body surface,boundary element method(BEM)is adopted to solve the boundary value problem(BVP),and the free surface is updated by time stepping scheme.The auxiliary functions are used to calculate wave loads.As the same time,for the stability of numerical simulation,the damped wave method is used to eliminate the waves far away from structures and avoid wave reflection.In this paper,the two dimensional solitary waves induced by a submerged elliptical cylinder moving with constant speed in shallow water have been simulated firstly.Comparing with the existing results and its convergence study,the numerical code has been verified.The process of the generation and development of successive solitary waves have been described in detail and the features of velocity fields have been analyzed.The influences of shape and speed of the elliptical cylinder on the wave profiles of solitary waves have been considered.The generated solitary waves have been used to simulate the head-on collision between the same and different successive solitary waves,and the elevation of the wave profiles and the characteristics of the flow field during the collision have been described.Studies have shown that the essence of the propagation and collision of solitary waves is the process of energy propagation and the process of energy conversion and balance between kinetic energy and potential energy.When the structure moves near the free surface,it will be affected by the wind,waves and current,and also be affected by the bottom in shallow water.A numerical model for the coupled motion between two-dimensional submerged cylinder and the nonlinear wave has been established based on the boundary element method.The paper simulated the motion of the cylinder under the influence of the wave in finite or infinite water deep.The different influences of infinite and finite water deep on the motions of the cylinder have been analyzed.Then,the influences of wavelength,amplitude,the water deep and the initial conditions on the motions of the submerged cylinder have been analyzed.Finally,using the previous research results,the coupling motion between the cylinder with the successive solitary waves have been simulated,and the difference between the solitary wave and Stokes wave have been analyzed.