旋转射弹高速倾斜入水多相流场与弹道数值模拟

基于VOF多相流模型和有限体积法求解水、汽、气多相流动的RANS方程，结合重叠网格技术和six DOF算法对某一型号舰载射弹倾斜入水过程进行数值模拟研究。首先基于该方法研究了射弹旋转效应对射弹运动特性及流体动力特性的影响，然后对不同入水角下倾斜入水过程进行分析，得到不同倾角下旋转射弹入水空泡形态发展规律、弹体运动特征及流体动力特性变化规律。研究结果表明：射弹的旋转有利于弹体在初始对称面内的弹道稳定性，但会降低弹体侧向稳定性，使射弹受到的阻力系数、俯仰力矩系数变小；入水角越小，形成的空泡越不对称，由射弹运动状态的改变引起的空泡形态变化越明显，在超空泡航行阶段，弹体运动较稳定，不同角度下流体动力系数差别很小，当弹体下表面刺破空泡壁沾湿时，弹体运动状态发生较大变化，流体动力系数迅速增大，此时入水角度过小，弹体容易失稳；弹体的沾湿对空泡形态、弹体运动稳定性和流体动力特性有着重要的影响。

Numerical simulation of multiphase flow field and trajectory of high-speed oblique water entry of rotating projectile

The numerical simulation of oblique water entry of a certain type of ship-borne projectile at high speed was performed. The FVM method and the VOF multiphase flow model were introduced to solve RANS equations, and the overset mesh and six DOF algorithms were used to achieve the coupling solution of the movement of projectile and the multiphase flow field. Based on this method, the influence of projectile rotation effect on the projectile motion characteristics and hydrodynamic characteristics was firstly studied. And then the cavitation morphology, the ballistic and hydrodynamic characteristics during the oblique water entry of the rotating projectile at different inclination angles were analyzed. The simulation results shows that the rotation of the projectile is beneficial to the ballistic stability of the projectile in the initial symmetric plane, but it reduces the lateral stability of the projectile. The rotation of projectile reduces the drag coefficient and pitching moment coefficient of the projectile. With smaller initial water entry angle, the cavitation shape was more asymmetric, and the change of cavitation shape caused by the change of projectile motion state was more obvious. At the stage of supercavitation, the motion of the projectile was relatively stable, and the hydrodynamic coefficients has minor difference at different angles. When the lower surface of the projectile pierced the cavity wall and wetted, the motion state of the projectile changed greatly and the hydrodynamic coefficients increased rapidly, and at this stage, the projectile are prone to becoming unstable if the water entry angle is too small. The wetting of the projectile has an important influence on the cavitation shape, motion state and stability of the projectile.