基于重叠网格方法浮筒涡激运动特性数值分析

浮筒被广泛应用在海洋工程中,研究浮筒的涡激运动对于减少其对海洋平台构件的疲劳损坏具有指导意义。传统的动网格方法在处理浮筒转动运动时会因网格变形过大导致计算不收敛,采用了重叠网格方法以解决这一问题。数值试验采用了基于开源工具包Open FOAM自主开发的naoe-FOAM-SJTU求解器。分别进行了自由衰减数值试验和涡激运动数值试验。研究表明,随着折合速度的增加,浮筒的顺流向、横流向、垂荡和艏摇运动频率增加,且顺流向与垂荡频率相近,横流向与艏摇频率相近;其次,根据涡量场分布,表明浮筒前一时刻的泻涡会影响到浮筒之后时刻的周向涡量分布;最后,研究发现自由端对于浮筒尾流场泻涡有着显著影响,为将来探究减少浮筒涡激运动的方法提供指导。

Investigation on the characteristics of vortex-induced motion of buoyancy can based on overset grid method

Buoyancy can is widely applied in ocean engineering. The investigation of the large-amplitude motion of the buoyancy can is instructive for reducing the fatigue damage of the offshore platform components. The conventional deforming mesh is not able to perform large amplitude rotation due to the excessive mesh distortion. In this paper, the overset grid method is used to solve this problem. The solver applied in the numerical experiments is the naoe-FOAM-SJTU solver based on the open source toolkit OpenFOAM. In this study, the free decay tests and VIM tests at different inflow velocities are carried out. The results show that with the increase of the inflow velocity, the frequency of inline, crossflow, heave and yaw motions increase, and the inline and heave frequencies are similar, and crossflow and yaw frequencies are similar. Secondly, according to the vortex field distribution, it shows that the previous vortex affects the circumferential vortex field distribution during the motion cycle. Finally, it is found that the free end of the buoyancy can have a significant effect on the pressure distribution of flow field, which provides guidance for reducing the VIM of the buoyancy can.