自适应动网格在流体-浮体耦合运动中的应用

Application adaptive dynamic grid to coupled motion of fluid and floating body

为了解决流固耦合问题中物体大幅度运动带来的困难,更精确地计算波形变化和物体的受力,用任意拉格朗日-欧拉方法导出了带自由表面的流固耦合运动计算模型。在计算过程中用动网格方法跟踪浮体的运动,并用自适应网格在自由表面附近进行加密。计算了无粘流体、粘性流体中浮体的运动规律,并与理想弹簧-物体振动模型理论解进行了比较,同时计算了浮体在粘性流体中的侧倾振荡。结果表明,在无粘流体中浮体的垂直振荡与理论解符合得较好;在粘性流体中物体的运动为阻尼振动,与实际相符得较好。浮体在粘性流体中的侧倾振荡为阻尼运动,其侧倾角度随时间的增加而减小,在小角度时侧倾振荡与理论解接近。计算结果验证了计算程序的可靠性与精度,为ALE(arb itrary lagrang ian eu lerian)方法应用于流体-多浮体耦合运动分析奠定了基础。

In order to overcome the difficulties of the large amplitude motion of floating body in fluid field and to compute wave profile and forces acting on solid body more accurately, ALE （arbitrary lagrangian- eulerian） method was used to build the mathematical model of fluid-solid coupled motion with free surface. The dynamic grid was applied to tracking the motion of the floating body. The adaptive grid was utilized to fine the grids near the free surface. The motions of floating body coupled with inviscid and viscous fluid were calculated and compared with the analytical ones from spring-object vibrating model. The swaying with initial list angle of the floating body coupled with viscous flow was also computed. The results show that the heaving of the floating body in inviscid flow well agrees with the one from the spring-object vibration model. In viscous flow, the agreement between the heaving of the floating body and the practical one was sound because it was the damping vibration, and the angle of list decreased with the time. The list vibration of the floating body well agrees with the one from the theory in the case of small angle. The results show that the computational program is reliable and accurate. The job laid a foundation for application of ALE method to analyzing fluid-multibody coupled motion in the future.