An investigation on the wake vortex structure and trajectory characteristics of the vehicle launched underwater

The Improved Delayed Detached Eddy Simulation (IDDES), VOF (Volume of Fluid) multiphase flow model, and overlapping grid technology were adopted in this paper. The results show that the interaction between the high-speed regions and the low-speed flow increases, as the Kelvin–Helmholtz instability phenomenon occurs in the mixing fluid during traveling underwater. Under the effect of the inertial force, the tail bubble expands successively, resulting in an increase in cavity volume and a decrease in pressure. In addition, the wake vortex is composed of the main vortex and secondary vortex, which is a cone of the major influencing factors causing the disturbance of the flow field. As the vehicle continuously passes through the free surface, the buoyancy center of the vehicle successively moves downward, resulting in a change in the direction of buoyancy moment and aggravating the deflection amplitude of the vehicle.