基于OpenFOAM的液舱在波浪中运动特性研究

Motion characteristics of liquid tank in waves based on OpenFOAM

当船舱内部分别载有水和冰时,每个水质点具有不同的加速度,而所有冰质点具有相同的加速度,这将导致相同质量水舱和冰舱具有完全不同的运动特性。基于开源软件OpenFOAM模拟二维液舱和冰舱在波浪中的运动过程,通过将载水舱与含有等质量冰的载冰舱的计算结果进行比较,研究液舱内水运动对于液舱运动特性的影响。建立以N-S方程和连续性方程为控制方程的计算模型,采用有限体积法(FVM)离散控制方程,采用流体体积法(VOF)捕捉自由液面,采用动网格技术处理物体运动所导致的网格变形。研究舱内水或冰,外部波浪与液舱的相互作用,分析三者之间的耦合作用机理。研究发现,相同质量的水和冰发生状态转化以后固有频率发生了显著的变化,因此船舱固有频率和波浪频率的相对关系发生变化,进而影响载水舱和载冰舱的运动幅值。

When the tank is filled with liquid and ice respectively,each particle of fluid has a different acceleration,but they are all the same for the ice,which will lead to the motion characteristics of inner liquid is quite different from that of the ice.In this paper,the process of two-dimensional liquid tank and ice tank pitching in waves will be simulated based on the open source software OpenFOAM.The comparison between air and water is made,to investigate the influence of inner liquid on the motion of the tank.The numerical model is established based on the N-S equation and the continuity equation,the finite volume method(FVM)is used to discretize the control equations,the fluid volume method(VOF)to capture the free surface,and the dynamic mesh technology to deal with the mesh deformation caused by the moving of body.The mutual dependence between inner liquid or ice,waves and the tank are investigated.It is found that the natural frequencies of water and ice are much different,their differences from wave frequency also get changed,which will further affect the motion amplitude of water tank and ice tank.