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

超空泡射弹异步并联倾斜入水空泡演化与运动特性分析

¹ School of Mechatronics Engineering, North University of China, Taiyuan 030051, China
² School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China

Received: 27 February 2023

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.

摘要

基于VOF多相流模型与重叠网格技术建立了超空泡射弹异步并联倾斜入水数值方法, 利用单发射弹倾斜入水实验对数值方法的有效性进行了验证, 在此基础上, 分别对不同初始间距及入水顺序下前后两射弹的空泡演化与运动特性进行了数值模拟与分析。研究结果表明: 对于前发射弹, 在初始间距为0.5倍弹长时, 由于受到后发射弹空泡剧烈挤压, 前发射弹无法产生完整空泡包裹弹体, 运动受到严重影响并最终失稳; 同时, 前发射弹自上侧入水与自下侧入水相比, 其空泡受到的挤压程度更大, 沾湿更早且失稳更快; 随着初始间距的增大, 前发射弹附近空泡受后发射弹的影响减弱, 2种入水顺序下均运动平稳。对于后发射弹, 由于前发射弹空泡的持续作用, 其空泡始终不对称, 运动稳定性受到影响, 在间距为0.5倍弹长时向内侧偏转失稳, 在间距为1倍弹长时运动平稳, 间距为2倍和3倍弹长时向外侧偏转失稳, 且2种入水顺序下运动规律基本一致。