Abstract
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.
Highlights
Water entry refers to the process in which a projectile penetrates a free surface of water with a given initial velocity
The rotational speed of the projectile has a direct effect on the stability of the trajectory and the flow characteristics at water entry
The water-entry problem for a high-speed projectile has been investigated numerically using the Z–G–B cavitation model and the Stress Transport (SST) k–ω turbulence model based on the Reynolds-averaged Navier–Stokes (RANS) method
Summary
Water entry refers to the process in which a projectile penetrates a free surface of water with a given initial velocity. For high-speed projectiles, the water-entry process is associated with the appearance of strong turbulence, multiphase flow, generation of an impact force, and cavitation phenomena, and these have a significant influence on the characteristics and stabilities of the trajectory of a projectile. With regard to numerical simulations, there have been a number of studies of impact forces, hydrodynamic characteristics, and water-entry cavity dynamics.. The high-speed water-entry problem poses an important challenge and is in urgent need of further study. In this paper, a detailed analysis of this problem is performed through three-dimensional numerical simulation of water entry by a high-speed projectile. The influences of rotational speed, initial velocity, and water-entry angle of the projectile on the stability and characteristics of its trajectory are investigated in detail
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