High speed water entry phenomenon comparison of projectile with free and constant speed

Abstract

The high-speed water-entry phenomenon of vehicles with a free and constant speed is numerically studied. The different behaviors of the cavities created by the vertical water entry of projectiles with different nose shapes, tail shapes, and impact speeds are investigated. The drag characteristics of the projectiles with a free or constant impact speed are compared. The flow characteristics of the flow field are compared and analyzed. Unlike the cavity induced by free-speed water entry, that induced by constant-speed water entry is more stable and is maintained for a longer time. The expansion of the projectile tail can weaken the effect of the re-jet flow, generated by the cavity seal, on the head of the cavity and prolong the attachment time of the cavity. The shape of the projectile tail can cause drag disturbance, but the key factor determining the drag of the projectile mainly depends on the water entering speed and the nose shape of the projectile.