规则波中船舶骑浪运动条件及失稳特性分析

Analysis of the conditions of ships′surf-riding and its instability in regular waves

针对船舶在规则波中纵荡运动稳定性问题,本文基于非线性动力学方法研究船舶骑浪运动的动力特性,建立了纵浪条件下船舶纵荡运动方程。以某内倾船为例,分别采用梅林科夫方法和龙格库塔方法求解纵荡运动方程。通过梅林科夫函数阈值图,得到船舶发生骑浪运动的速度临界值。基于数值计算,分别绘制船舶骑浪时和未骑浪时的时历曲线和运动相图,并分析骑浪失稳特性;以螺旋桨转速为分岔参数作船舶骑浪运动分岔图,分析了船舶骑浪运动的失稳条件。结果表明:当波幅较大时,船舶发生骑浪运动的螺旋桨临界转速降低。当船速与波速相近时,若波陡足够大,船舶容易发生骑浪现象。

For the stability of the ship surge motion in regular waves,the dynamic features of ship surf-riding motion are studied based on the nonlinear dynamic method.The surge motion equation is established in a longitudinal wave scenario.Taking a tumblehome ship as an example,the surge equation is solved by adopting the Melnikov method and Runge-Kutta method.The critical ship speed under the surf-riding motion is obtained according to the threshold figure of the Melnikov function.The time histories and phase diagrams are drawn when the ship is in surf-riding and non-surf-riding scenarios,and the surf-riding instability characteristics are individually analyzed based on numerical simulations.Taking the revolution speed of a propeller as the bifurcation parameter to draw the ship surf-riding bifurcation diagram,we analyze the instability conditions of the ship surf-riding motion.The results show that the critical revolution speed of the propeller corresponding to the surf-riding motion is decreasing when the wave amplitude is large.When the ship′s speed is approximately equivalent to the wave speed,the surf-riding phenomenon will occur if the wave steepness is large enough.