Load and motion behaviors of ogive-nosed projectile during high-speed water entry with angle of attack

Abstract

Hazardous loads exist not only during the water impact but during the entire high-speed water entry process. This article systematically investigates the load behavior of an ogive-nosed projectile during the entire process from the impact to the full wetting by experimental and numerical methods. It is found that the hazardous loads during the entire water entry process mainly exist in the three stages of water impact, tail slap and beginning of wetting. The formation mechanisms of hazardous loads are revealed. The initial angle of attack (IAA) within 8° in absolute value has little influence on the axial load, with the maximum difference of 4 g. In contrast, the effect of the IAA on the radial load is significant in terms of the direction, the peak, the beginning time of wetting, and the magnitude after wetting. The peak radial load of the tail slap reaches 3.7 times the peak axial impact load at the IAA of −8°. When the IAA is large (±8°), serious deflection of the trajectory occurs, such as the water exit at +8° and the backward movement at −8°; the angle of attack eventually diverges; and the pitch angle change reaches over 200°. The results provide helpful guidance in effectively identifying all hazardous loads during the entire water entry process and clearly understanding the motion behavior under the action of the loads.