Numerical investigations of trajectory characteristics of a high-speed water-entry projectile

A detailed analysis of the characteristics and stability of the trajectory of a high-speed projectile during water entry is investigated numerically. The Zwart–Gerber–Belamri cavitation model and the shear stress transport k–ω turbulence model based on the Reynolds-averaged Navier–Stokes method are employed. The numerical method is validated by comparison of its results with the experimental images of cavity shape and with measurements of the penetration distance. Using this numerical method, the influences of rotational speed, initial velocity, and water-entry angle of the projectile on the stability and characteristics of its trajectory are investigated. The variations in projectile trajectory, total drag, and velocity reduction are analyzed. In addition, the cavity characteristics at water entry are presented and analyzed. The results show that the rotation of the projectile has an adverse influence on the stability at water entry, although the magnitude of the rotational speed has little effect on the reduction in projectile velocity. The initial velocity of the projectile has a direct effect on the trajectory stability. It is also found that in practice, there should be a critical water-entry angle for the stability of a projectile.