Numerical research on the effect of front body on water-entry load of a projectile

When the projectile passes through the gas-liquid interface, the sudden change of density may cause a violent impact load and do untold damage to it. It seriously affects the working effect of the projectile. In order to reduce the water entry load of the projectile, based on Rabbi’s idea of load reduction, a kind of structure of projectile with front body was proposed. The S-ALE (structured arbitrary Lagrange-Euler) algorithm and the fluid-structure coupling method with penalty function were used to simulate the shape of the cavitation wall and the projectile motion state, which is coincident by comparing with those of experiments. The validity of the numerical method is verified. Furthermore, the influence of the water entry angle of front body, the dimensionless water entry time interval parameter between main projectile and front body, the size of front body, the initial water entry velocity of main projectile and front body on impact load were researched by numerical simulation. The simulation results show that the front body will impact the main projectile when they both entering water vertically, which increases the impact load due to the collision of them. When the front body enters the water obliquely and the main projectile still enters the water vertically, the collision between main projectile and front body could be avoided and a good load reduction effect is obtained. The maximum load reduction ratio is up to 90%. The dimensionless time interval parameter range for obtaining a good load reduction effect is from 0.8 to 0.9. Within this range, variation laws of the water entry load of main projectile with the size of the front body and the initial velocity of entering water were discussed in detail. The effect of load reduction increases with the increase of the size of the front body and the initial water entry velocity. © 2023 Explosion and Shock Waves. All rights reserved.