Cavity evolution of ventilated vehicle launch under a rolling condition

Abstract

The unsteady development of the tail cavity of a vehicle after it leaves a tube often causes adverse effects, most notably an impact load on the vehicle when the cavity ruptures. The rolling of the launch platform can alter the development of the tail cavity, significantly altering the influence of the impact load on the motion and attitude of the vehicle. The present study employs the shear stress transport k-w model, the volume of fluid multiphase flow model, the Schnerr–Sauer cavity model, and the overlapping mesh technique to conduct numerical simulations of the underwater launching process of a ventilated vehicle under both stationary and rolling boundaries. A comparative analysis is conducted to examine the evolution of the cavity shape, pressure distribution, and collapse-induced load in the tail cavity under various conditions after vehicle launch. The findings suggest that the rolling of the tube induces an asymmetrical development of the shoulder cavity lengths and widths on both the windward and leeward sides, with the result of a lower peak pressure at the cavity closure position compared with that under stationary conditions. The rolling of the tube reduces the internal velocity within the tail cavity, elevates the rupture position of the tail cavity, delays the tail cavity rupture, impacts the timing of the force peak occurrence in the vertical direction of the vehicle, reduces the high pressure at the point of tail cavity rupture, and modifies the post-rupture structural characteristics of the tail cavity.