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.