Numerical Calculation and Analysis of Supercavitation Formation Characteristics of High-speed Projectile

Abstract

Based on the homogenous equilibrium multiphase-flow theory, the mathematical model of the supercavitation formation process of underwater high-speed projectile was established. The underwater shooting experiment of the 12.7 mm caliber projectile was carried out to verify the rationality of the model. Numerical simulations were carried out for 76 mm projectiles of different velocities. The results show that, on the surface of the projectile, cavitation occurs in sequence along the axis. In the region of the projectile head, the water vapor content increases linearly at each point. In the cylindrical region of the projectile, the water vapor content at each point rises rapidly to 0.3~0.4 and then maintains the plateau period, and then rises rapidly. The faster the projectile is, the shorter the plateau period is, the more quickly the supercavitation forms, and the supercavitation formation time satisfies exponential change law. In the projectile head region, the change process of the cavitation growth rate can be divided into two stages, from a fast linear decay phase to a phase that approximately slowly linearly attenuates. The faster the projectile is, the higher the rate of cavitation development, and the faster the attenuation in the first stages, the greater the attenuation, and the decay rate in the second phase is almost constant. In the cylindrical part of the projectile, the change process of the cavitation growth rate can be divided into two stages, a fast decay stage and a slow decay stage. The faster the projectile is, the higher the rate of cavitation development, and the faster the attenuation in the second phase. The variation characteristics of the viscous drag coefficient of the projectile surface corresponds to the cavitation characteristics of the projectile cylinder. The faster the projectile is, the more quickly the drag coefficient attenuates, and the smaller the value when it reaches stability. When the velocity is higher than 1 100 m/s, the time when the drag coefficient is stable is almost constant, and the value change is little when it reaches stability.