Hydrodynamic characteristics of the underwater continuous launching of vehicles under rolling conditions

Due to the influence of initial conditions such as the tethered velocity, vertically launched underwater vehicles generate large vortex structures in the wake after leaving the launch platform. This leads to an asymmetric surface pressure distribution on the second vehicles passing through the wake, adversely affecting their attitude. The rolling of the launch platform is another critical component of the above initial conditions. This study used the Realizable k−ε model, the volume-of-fluid multiphase flow model, and overlapping grid technology to numerically simulate the launch process of sequentially launched and retrogradely launched vehicles, both with and without rolling conditions. The study conducted a comparative analysis of the evolution patterns of wake vortex intensity, pressure distribution, and air–water phase distribution for the second underwater vehicles under different conditions after their launch. The results show that under rolling conditions, the wake vortex structure exhibits curling at both the vortex head and the vortex tail, with regions of greater vorticity shifting laterally. At certain moments, rolling and vorticity have similar effects on the surface pressure of the second vehicle. The presence of rolling accelerates the expansion and compression of gas pockets within the launch tube, reducing the disturbance of gas on the retrogradely launched first vehicle and changing the rolling angle of the vehicle. In the rolling conditions, the peak water hammer force on the inner wall of the platform increases and the forces acting on the inner wall of the tube show periodic variations.