航行体沾湿区域对空泡尾流结构的影响

The Influence of Wetted Area of Vehicle on the Wake Structure of Cavity

为研究航行体沾湿区域对通气超空泡尾流结构的影响,利用计算流体力学方法对超空泡航行体改变攻角过程中沾湿区域和空泡尾部涡量的非定常变化进行数值模拟。通过分析空泡尾部流场压力及涡量的变化,揭示了空泡尾部不同流动结构的转变机理。结果表明:在低弗劳德数条件下,空泡尾部双涡管的上下方存在高压区,受环境压力差的影响,下方压力大于上方,空泡双涡管之间的流动方向向上,形成一对中心上卷的双涡;随着航行体攻角的不断增大,沾湿区域使空泡形成了三涡管尾流结构,涡管下方高压区的压力比上方低,空泡下方双涡管之间的流动方向向下,形成一对中心下卷的双涡;空泡尾部双涡管到三涡管过渡过程中,空泡尾部上下方的压力及流速大小发生交替改变,从而形成了四涡管尾流结构。

In order to study the influence of wetted area of vehicle on the wake structure of ventilated supercavity,the CFD method was used to simulate the unsteady variations of the wetted area and the vorticity in the wake of a supercavitating vehicle in the process of changing the angle of attack. The transformation mechanisms of different flow structures in the wake of a cavity are revealed by analyzing the changes of pressure and vorticity in the wake flow field. The results show that,under the low Froude number,a high pressure zone exists above and below a twin-vortex tube at the tail of cavity. Due to the influence of environmental pressure difference,the pressure below the tube is higher than that above it. The flow direction between the two vortices is upward to form a pair of twin vortices rolled up in the center. With the increase in the angle of attack of vehicle,the wetted area causes the cavity to form the wake structure of three-vortex tube. The pressure in the high pressure area below the vortex tube is lower than that above it,and the flow direction between the two vortices below the cavity is downward to form a pair of twin vortices rolled down in the center. During the transition from the twin-vortex tube to the three-vortex tube,the pressures and velocities of the upper and lower parts of cavity wake change alternately,thus forming the wake structure of four-vortex tube.