二维浮体在聚焦波浪作用下的高频共振响应研究

Research on ringing of a two dimensional floating body induced by focused waves

基于势流理论建立二维完全非线性数值波浪水槽模型,利用该模型对二维驳船结构在非线性聚焦波作用下的高频共振响应(ringing现象)进行了研究.引入高阶边界元方法解决边界值问题,应用混合欧拉-拉格朗日方法和四阶龙格库塔法模拟结构物与波浪的相互作用.引入虚拟函数法耦合求解波浪载荷与物体运动.文中对聚焦波浪的传播特性进行了数值模拟,并将数值结果与试验值进行了对比验证.基于完全非线性数值波浪水槽,研究了聚焦波浪与结构物的相互作用问题,研究结果表明当聚焦波浪主频的三倍频等于或接近物体横摇方向固有频率时,物体在横摇方向将会产生ringing现象,在聚焦波浪经过浮体之后浮体仍会以高频振动的方式持续运动,进一步分析表明导致浮体发生ringing现象的入射波频率范围较大,在海洋结构物设计中应尽量避免入射波浪的三倍频接近浮体的固有频率.

A resonant behavior of the roll motion of a two dimensional(2D)floating barge induced by nonlinear focused waves is investigated by velocity potential theory.The higher order boundary element mothed(BEM)is adopted to solve the boundary value problem.The mixed Eulerian-Lagrangian(MEL)technique and the 4 th-order Runge-Kutta time stepping scheme are used to simulate the interaction of waves and the floating barge.The auxiliary functions are introduced to calculate wave loads and the coupled motions.In this paper,numerical results of the propagation of focused wave are presented with the verification through the experimental results.Focused wave-structure interaction is analyzed based on the fully nonlinear numerical wave tank,and the results indicate that the roll motion principally excited by higher harmonic wave loads when the triple dominant wave frequency is equal to the natural frequency in the rolling direction and the body will continue to move with high frequency vibration after the focused wave passed the floating body.Further analysis shows that the frequency range of the incident wave that caused high-frequency resonance of the body is relatively large.Therefore,it is necessary to avoid the triple frequency of the incident wave close to the natural frequency of the floating body in the design of marine structures.