6750箱集装箱船非线性波激振动和颤振响应分析

本文采用三维时域非线性水弹性方法分析了一艘6750箱集装箱船的水弹性响应以及运动和垂向弯矩特征。通过考虑入射波力、静水恢复力、砰击效应的非线性,研究了在恶劣海况下船体的非线性运动和垂向弯矩响应,同时分析了波激振动及颤振对垂向弯矩的影响。数值计算结果表明:(1)非线性入射波力对运动的影响较小,但是对垂向弯矩的影响较大,使得其有明显的倍频成分,同时中垂弯矩显著大于中拱弯矩。另外,非线性入射波力也引起了明显的非线性波激振动;(2)非线性静水恢复力对运动和载荷的影响均较大,但是没有引起明显的非线性响应。非线性计算的垂荡响应小于线性结果,而纵摇和垂向弯矩响应大于线性结果;(3)砰击效应对运动的影响较小,但对垂向弯矩的影响较大,砰击效应引起了显著的船体弹性高频振动,增大了载荷幅值,但是其引起的合成中垂和中拱幅值相差不大;(4)非线性水动力的作用主要引起垂向弯矩的倍频响应,包括倍频可能引起的二节点垂向弯矩弹性共振,而砰击效应主要引起船体二节点垂向弯矩共振;(5)本文的非线性水弹性响应计算结果与Kim给出的数值计算结果吻合很好。

Study on nonlinear springing and whipping of a 6750 TEU container ship

The hydroelastic responses,motions and loads of a 6750 TEU container ship are investigated by using 3D nonlinear hydroelastic method in time domain.The nonlinear motions and vertical bending moment at amidship are calculated by considering nonlinear Froude-Krylov exciting force,nonlinear hydrostatic re?storing force and slamming force.At the same time,the influence of springing and whipping on vertical bend?ing moment is analyzed.It is concluded that:(1)The nonlinear Froude-Krylov exciting force has slight influ?ence on motion,but large influence on vertical bending moment.There are obvious nth-order components in the vertical bending moment,and the sagging VBM is larger than hogging VBM.The apparent nonlinear springing is induced by the nonlinear Froude-Krylov exciting force;(2)The nonlinear hydrostatic restoring force has large influence on motion and vertical bending moment,but there are no nonlinear response compo?nents.The nonlinear result of heave is smaller than the linear result,but the nonlinear result of pitch is larger than the linear result;(3)The slamming force has slight influence on motion,but large influence on vertical bending moment.And the hull structural elastic vibration in high frequency is induced by slamming,which enlarges the amplitude of vertical bending moment,but there is little difference between combined sagging VBM and combined hogging VBM;(4)The nonlinear hydrodynamic effect mainly causes the nth-order re?sponses of VBM including elastic two-node vertical bending mode vibration.But the slamming force only in?duces two-node vertical bending mode vibration;(5)The nonlinear hydroelastic responses in the paper are in good agreement with the results of Kim.