Research on the interference characteristics of successively launched underwater projectiles

Abstract

In the successive underwater launch of two projectiles, wake vortices shed from the leading projectile have significant effects on the subsequent projectile's hydrodynamic forces, attitude, and trajectory. Herein, experimental research is conducted by successively launching two underwater projectiles at prescribed transport velocities using embedded inertial measurement units to record acceleration data simultaneous with a high-speed camera to visualize the cavity behaviors. After a trial error evaluation, the interference between two conical-nosed projectiles is shown to increase as wake vortices develop from dispersed vortex rings at low transport velocities into continuous counterrotating vortex pairs at high transport velocities. Thus, the second projectile experiences less lateral movement and rotation than the first projectile at u > 0.1 m s−1. The effect of the nose shape is also studied by conducting experiments on ellipsoidal-nosed projectiles, whose trends are similar to those of the conical-nosed projectiles. A quantitative comparison of the interference shows that the ellipsoidal-nosed projectiles experience more interference than the conical-nosed projectiles due to the absence of the shoulder cavity.