Hydrodynamic characteristics of sequential water entry for two structures under different time intervals

To investigate the high-speed water entry problem of sequential structures, a three-dimensional numerical calculation model for the high-speed water entry of sequential structures was established based on solving the Reynolds-averaged Navier–Stokes equations. The volume of fluid multiphase flow model and 6 degrees of freedom rigid body motion model were employed, and the Schnerr–Sauer cavitation model was introduced, combined with overlapping grid technology. Numerical simulations of sequential water entry for two structures under different water entry time interval were carried out, and the influence laws of different water entry time interval on the cavity evolution, vortex evolution, and motion characteristics during the water entry of sequential structures were obtained. Results show that the influence of sequential water entry on cavity evolution is mainly reflected in three aspects: disrupting cavity formation, influencing surface closure of the cavity, and inducing curvature in the cavity wall. Simultaneously, the conventional vortex evolution has been modified, with impact dissipation emerging as a novel mode of vortex evolution within the small water entry time intervals. Moreover, in comparison to the water entry of the first structure, the second structure experiences significantly less resistance upon immersion in the flowing water, leading to a more gradual deceleration.