关键词: 跨介质流动, 力载荷, 多相界面, 重叠网格, 涡量分析

Abstract: The force load exerted on the vehicle and the surface pressure exist a essential nonlinear behaviour and present a time-varying characteristic due to the complicated multiphase flow in the process of the vehicle crosses the water-air interface. For the load feature and the multiphase interface evolution, a force load measurement and multiphase interface visualization experiment is designed. A numerical framework, which adoptes the VOF (volume of fluid) multiphase model coupled with the overset mesh is applied to verify the experiment scheme. The force load, changed phase interface, pressure and vortex structure evolution under different maximum depths of water entry and the rotation speeds are simulated. The simulation results indicates that the force load in the upstream face plays a main role compared with that in another two directions, and its evolution shows a quasi-symmetric characteristic with the depth of water entry. In addition, the increased rotation speed enhances the force loads exerted on the vehicle. The high-pressure region always exists on the head of vehicle and the low-pressure region is distributed on the shoulder. And the influences of maximum depth of water entry on the pressure peak are limited. The distribution of streamline illustrates the complexity of the trans-medium flow, and the velocity peak exists in the tail of vehicle. The vortex structure will generate differentiation, growth, dissipation and extension due to the changed motion state and the action of different fluid in the trans-medium process. Besides, the decreased maximum depth of water entry result in more complex multiphase interface, vortex structure scale and vortex evolution characteristics.

Key words: trans-medium flow, force load, multiphase interface, overset mesh, vorticity analysis