大攻角水下航行体自然空泡流的数值模拟研究

基于相分数输运方程型的均质平衡流空化模型,采用有限体积法研制了大型空泡流计算程序,对大攻角下运行的水下航行体三维空泡流进行了数值模拟,并与实验结果进行了对比.首次将非线性涡粘湍流模式与基于Rayleigh-Pies-set方程的TEM型空化模型相结合,建立了自然空泡流的数学模型.采用基于SIMPLE的压力-速度-密度耦合修正算法、二阶精度三时间层格式以及基于延迟修正的高阶对流TVD格式.计算模拟了0.2～0.6空化数、4°～20°攻角的不同工况,得到的三维空泡形状及压力分布与实验结果相符.研究了大攻角下航行体周向上的空泡形态分布特征,给出了多种空泡尺度和升阻系数与空化数和攻角之间的关系.通过定量分析发现,空泡的不对称性导致航行体某些部位受力集中,表明高速带空泡运动的航行体在大攻角运动中其结构将受到巨大的水动力载荷.计算还发现,大攻角下的阻力系数与空化数之间的关系和零攻角条件下刚好相反,并根据空泡的不对称性从形状阻力与粘性阻力的关系上对这种现象作出了解释.

Modeling and Simulation of Cavitating Flow over Underwater Vehicle with Large Angle of Attack

A Homogenous-Equilibrium-Model based computation code was developed by using the FVM,to numerically research three-dimensional large-attack cavitating flow around underwater vehicle. Non-Iinear eddy-viscosity turbulence model and Rayleigh-Plesset equation deriving cavi-tation model were used together. Full field density, pressure and velocity distributions at different cavitation number and different attack were computed systematically. Primarily, the computed cavi-ty shapes and pressure distributions along the pressure side and suction side were compared with experimental results to find generally good agreement,including the coincidence at some detailed parts of cavity.Secondly,the relations of different cavity dimensions to cavity number and attack were investigated and some useful conclusions were obtained. Afterward, the total force acting on vehicle body was studied to qualitatively explain why the body may get damaged in navigation when cavitation occurs. Finally, it was discovered interestingly that, the drag-force variation trend along with cavitation number at attack conditions was completely opposite to that at zero-attack condition. Such phenomenon was explained theoretically from the relationship between profile-drag and viscous-drag due to the asymmetry of cavity shape.