液舱晃荡与船体耦合运动的全非线性数值模拟与分析

Fully nonlinear numerical simulation and analysis of sloshing and coupling ship motion

为了研究液舱晃荡流对驳船运动的非线性耦合影响,本文采用边界元法在时域中模拟了二维驳船在波浪和晃荡载荷作用下的三自由度运动。数值模拟过程中采用半混合欧拉-拉格朗日方法(Semi-MEL)实时更新瞬时自由液面,应用辅助函数法求解速度势的时间导数。在上述数值基础上,对入射波、船体运动和晃荡流的非线性耦合关系进行解耦计算。所求驳船运动响应的数值计算结果与实验结果吻合良好,验证了该数值方法的准确性。通过分析不同入射波频、波幅和液舱充液率条件对驳船运动幅值响应(RAOs)的影响,可得出液舱晃荡作用力与波浪激振力的耦合作用决定了驳船的横荡、横摇运动RAO的大小;在晃荡运动的一阶共振频率附近,横荡、横摇运动RAO均为最小值;相比横荡运动,对横摇运动而言,最重要的耦合影响是RAO曲线由单峰值变化为双峰值;随着入射波幅的增加,晃荡诱导力矩的非线性变化导致了船体非线性的横摇运动。

In order to investigate the coupling effects of tank-sloshing flow on barge motion,the three degrees-of-freedom(DOF)motion of a two-dimensional barge under wave action and sloshing loads was simulated by the boundary element method(BEM)in time domain.The instantaneous free surface was tracked by semi-mixed Euler-Lagrange method(Semi-MEL),and the time derivative of the velocity potential was solved by auxiliary function method.Based on the above numerical methods,the coupling interactions between wave actions,sloshing inside tank and ship motion were decoupled.The present method was well validated by comparing numerical solutions of barge motion responses with the experimental results.The effects of various wave frequencies,amplitudes and filling rates on response amplitude operators(RAOs)of barge motion were analyzed.It is found that the value of RAO depends on the nonlinear coupling effects of wave-excitation and sloshing-induced force,the minimum values of both the responses of sway and roll motion appear at the sloshing motion natural frequency,near which,the RAO of roll motion exhibits two peaks compared with that of sway motion,and that,with the increase of wave amplitude,the nonlinear variation of sloshing-induced moment results in the nonlinear roll motion of ship.