Experimental and numerical study on the time-varying load characteristic and flow instability in a rotated trans-media process

This study aims to present the time-varying load characteristics and flow instability in the rotated trans-media process of vehicle due to complicated multiphase flow and nonlinear behaviour. The fluid forces exerted on the vehicle in a series of experimental tests with different maximum water entry depth and water entry velocities, the involved force load, cavity trajectory, and multiphase flow evolution are obtained. Experimental results demonstrated that the force load in the direction of main motion (x_exp^′ direction in rotating coordinate system) plays a prominent role, and its evolution presents a quasi-symmetric characteristic with the entry depth. The force load in radial direction (z_exp^′ direction in rotating coordinate system) shows a similar change trend. Due to flow symmetry, the force load in symmetric direction (y_exp^′ direction in rotating coordinate system) fluctuates around zero. Simulated results indicate that the larger water entry velocity promotes the formation of more clear trajectory and leads to a more intense splash plume phenomenon. The vortex evolution is highly dynamic with rich structures and diverse development patterns, and is influenced by changed entry velocity and depth. Both entry velocity and depth also influence the pressure characteristics, and change the dynamics in liquid water refilling stage.