Trajectory and Cavitation Characteristics of High-Speed Projectiles at Small Angle of Water Entry

The cavitation phenomena and ballistic characteristics of high-speed rotating projectiles entering the water with a small angle were numerically studied. The VOF multiphase model was introduced to capture the vacuole interface and the free liquid surface. The Schnerr-Sauer cavitation model was used to simulate the generation and evolution of cavitation process. The motion of the missile was calculated by the overset mesh technique and the six-degree-of-freedom algorithm. Then the trajectory characteristics, cavitation evolution and hydrodynamic properties of projectile were studied in the process of small angle water entry. The bouncing and fluttering phenomenon of the high-speed spinning projectile with small water entry angle was preliminarily explored. The results showed that when the initial launching angle was too small, the posture of the projectile tended to change greatly, the asymmetric shape of the vacuole and the large wet area of the projectile caused the moving body to receive large fluid dynamics and moments; the motion of the projectile was unstable and resulted in the bouncing and fluttering phenomena. The analysis shows that the projectile is easy to get wet with too small water entry angle. The wetting of the projectile has a great influence on the hydrodynamics and the motion state of the projectile. The asymmetric wetting of the projectile is an essential factor for the instability of super-cavitation projectiles. © 2019, Editorial Department of Transaction of Beijing Institute of Technology. All right reserved.