基于CFD−非线性有限元双向耦合的集装箱船波浪下结构崩溃数值仿真

Numerical simulation of structural collapse of container ship in waves based on two-way coupling of CFD nonlinear FEM

[目的]充分考虑载荷非线性和物面非线性因素的影响,研究集装箱船在波浪下结构响应及动态结构崩溃模式。[方法]首先,基于CFD平台建立船舶水动力模型,采用重叠网格法实现船体水动力模型动边界网格与远场流体域的欧拉网格间的匹配,在流体全域内采用流体体积法模拟自由面非线性,在流场全域内求解三维N–S方程,实时求解非线性波浪载荷;然后,建立可模拟船舯崩溃行为的船舶非线性有限元模型,基于显式动力学非线性有限元法计算包含塑性和屈曲的时域崩溃响应;最后,实现水动力模型与结构有限元模型在湿表面上的流体压力和节点位移的传递,以此进行CFD求解器与非线性有限元求解器间的双向迭代耦合,并实时计算4600 TEU集装箱船结构崩溃过程中的非线性波浪载荷和结构崩溃响应。[结果]结果显示,在极端波浪下上部至中部结构广泛进入塑性状态,主甲板、舷侧板、甲板纵骨和舷侧纵骨等构件在波浪下出现明显的屈服及失稳,甲板纵骨和舷侧纵骨等骨材发生严重的侧向失稳,船体结构丧失了承载能力。[结论]所提方法可较准确求解结构响应及动态崩溃模式,可作为研究船舶结构崩溃响应的一种新方法。

[Objective]The structural response and dynamic structural collapse mode of a container ship in waves are studied by fully considering the effects of load nonlinearity and surface nonlinearity.[Methods]First,a hydrodynamic model of a container ship is established based on the CFD platform,and the overset grid method is used to realize matching between the dynamic boundary grid of the hull hydrodynamic model and the Euler grid in the far-field fluid domain.The volume of fluid method is used to simulate the nonlinearity of the free surface in the whole fluid domain,and the N–S equations in three directions are solved in the whole flow field domain so as to solve the nonlinear wave load of the ship in real time.A nonlinear finite element model of the ship that can simulate its collapse behavior is then established,and the time-domain collapse response of the ship including plasticity and buckling is calculated based on the explicit dynamic nonlinear finite element method(FEM).Finally,the transmission of fluid pressure and node displacement between the hydrodynamic model and structural finite element model on the wet surface are realized,and two-way iterative coupling between the CFD solver and nonlinear finite element solver is carried out to calculate the nonlinear wave load and structural collapse response during the structural collapse of a 4600 TEU container ship in real time.[Results]Under extreme waves,the upper to middle structures of the container ship are widely plastic,the main deck,side plate,deck longitudinal,side longitudinal and other components have typical yield instability under the action of wave loads,the deck longitudinal,side longitudinal and other structural members have serious lateral instability,and the hull structure loses its bearing capacity.[Conclusion]The proposed CFD nonlinear FEM can accurately solve the structural response and dynamic collapse mode,making it viable as a new approach to studying the collapse response of ship structures.