An investigation into horizontal water entry behaviors of projectiles with different nose shapes

In the present study, high-speed horizontal water entry behaviors of flat, ogival and hemispherical-nose projectiles were studied experimentally and theoretically. Particular attention is given to characterizing the projectile dynamics and the cavity evolution before a deep pinching starts. An analytical cavity model based on the solution to the Rayleigh–Besant problem was developed to describe the cavity dynamics of projectile water entry. Three parameters in the cavity model were discussed and determined theoretically and experimentally. Numerical simulations using the AUTODYN-2D Lagrange–Euler coupling techniques were conducted to specially study the drag coefficients of projectiles. Based on the experimental and numerical results, a drag coefficient model independent on the cavitation number was proposed. The results indicated that there are two variation laws for the three parameters in the cavity model; Additionally, the drag coefficients increase with the impact velocities with holding the projectile nose constant and decrease with an increase in the projectile nose coefficient (CRH) value. Good agreements were observed between analytical results and experimental observations.

► An analytical cavity evolution model was developed.
► Three parameters in the cavity model were discussed and determined.
► Two variation laws were found for the three parameters.
► A drag coefficient model independent on the cavitation number was proposed.
► The average cavity wall velocity keeps constant in the water entry process.