Unsteady cavitation around submerged and water-exit projectiles under the effect of the free surface: A numerical study

Abstract

The growth, shedding, and collapse regime of cavitation under the effect of a free surface is complicated by projectiles moving near and across the free surface and three phases (air, liquid, and vapor due to evaporation) of a fluid. In this work, the flow behaviors of cavitation around projectiles moving beneath a free surface and exiting the free surface were numerically investigated in detail using a dual-time preconditioned Navier–Stokes (NS) model for three-phase flows. First, the cavitation flow structure around a submerged projectile moving parallel to the free surface at a constant velocity was computed to validate the numerical method. Comparisons between numerical and experimental data on cavity growth are presented. Second, the vertical and oblique water exits of the cavitating projectiles under different flow conditions were investigated. Special features of the flows, such as cavitation growth, shedding, and collapse under the effect of the free surface and the detailed pressure peaks on the surface of the projectiles from the collapse of the cavitation, were obtained, through which the physical mechanism of this flow was clearly observed. The findings are significant for the design and control of submerged vehicles and projectiles operating in such flow fields.