Analyzing cavity evolution and motion characteristics of asynchronous parallel oblique water-entry super-cavitating projectile

Abstract

Based on the volume of fluid multiphase flow model and the overset mesh technique, a numerical method for an asynchronous parallel oblique water-entry super-cavitating projectile was established. Experimental studies of the oblique water-entry of a high-speed single-launch projectile were carried out to validate the viability of the numerical method. The paper performed the numerical simulations and analyses of cavity evolution and motion characteristics of the front and rear projectiles in different initial intervals and in two sequences of top-side water-entry projectile first and bottom-side water-entry projectile first. The results show that when the initial interval of the first launch projectile is 0.5 time the projectile length, the first launch projectile cannot produce a cavity to completely encapsulate the projectile due to the violent squeezing of the following launch projectile cavity, and its movement is seriously affected and eventually loses its trajectory stability. At the same time, the first launch projectile that enters water from top side is squeezed to a larger degree than the one from bottom side, and the wetting phenomenon occurs earlier and loses stability faster. As the initial interval increases, the influence of the following launch projectile cavity near the first launch projectile is weakened, and the first launch projectile in both water entry sequences move steadily. For the following launch projectile, due to the continuous influence of the first launch projectile cavity, its cavity is always asymmetrical, and its motion stability is affected. The following launch projectile deflects to the inner side and destabilizes when the initial interval is 0.5 times the projectile length. When the initial interval is 1 time the projectile length, it moves steadily. It deflects to the outer side and destabilizes when the initial interval is 2 and 3 times the projectile length. In addition, the motion characteristics of the following launch projectile are basically identical in two water-entry sequences.