Effect of the different conditions between successively fired water-entry projectiles on the cavitation flow field and impact loading

摘要

The interaction of the flow field of multi-fired projectiles entering water has important research significance and application areas, such as anti-submarine rockets continuously attacking the same target in the water. In the paper, the cavitation flow field of different initial spacings between two successively fired water-entry projectiles was numerically simulated. The effect of the initial spacing on the projectile velocity and projectile loading, especially on the impact loading on the second projectile, is investigated. The results show that both the velocity and drag coefficient on the first projectile for different cases shows an almost same change trend and peak value before two projectiles collide together, although the existence of the second projectile will affect the cavitation flow field of the first projectile. Under different conditions, the maximal value of the drag coefficient in the collision stage is about 15 times of that of the projectile moving in the water. The initial spacing between projectiles has significant effect on the cavity, velocity change and impact loading of the second projectile. In the investigated cases, both the pressure peak at the head and maximal drag coefficient of the second projectile can be reduced by more than 90 compared with those of the first projectile. Correspondingly, the velocity reduction in the second projectile is much slower than that of the first one. After the projectile passes through free surface for 0.6ms, the velocity of the first projectile is reduced by about 25, while the velocity reduction in the second projectile is less than 6 of the initial velocity. In the investigated cases, three interaction patterns between two projectiles were observed, that is, direct-entry, “multi-phase-jet” interaction and upward jet interaction. With the interaction mode of direct-entry, no pressure peak on the head of the second projectile appears when it passes through the free surface. With the “multi-phase-jet” interaction mode, the pressure peak on the head of the second projectile is 3–6 times that with the upward jet interaction mode.