Numerical Simulation of Submarine Surfacing Motion in Regular Waves

Abstract

Submarine surfacing in wave’s environments is fully three-dimensional unsteady motion and includes complex coupling with hydrodynamic force and dynamic motion of the rigid body. This paper uses in-house computational fluid dynamics (CFD) code HUST-SHIP to solve RANS equation coupled with six degrees-of-freedom (6DOF) solid body motion equations. RANS equations are solved by finite difference method and PISO algorithm. Level-set method is used to simulate the free surface flow. Computations are performed for the DARPA SUBOFF model. The structured dynamic overset grid is applied to the numerical simulation of submarine surfacing motion in calm water, transverse regular waves with different ratio of wave height over submarine length, wave length over submarine length and surfacing depth over submarine length. The asymmetric vortices in the process of submarine surfacing can be captured in this study. The existence of the vortex generated during the submarine surfacing could cause the destabilizing hydrodynamic rolling moment. Relations among maximum roll angle, surfacing velocity and wave parameters are concluded by comparison with variation trend of submarine motion attitude and velocities of surfacing in different wave conditions. Simulation results confirm that wave height and wave length lead to surfacing velocity and roll angle changes, significantly. Maximum roll angle also increases with the increase in wave height and wave length. Maximum roll angle with wave height (h/L = 0.04) can reach to 7.29°, while maximum roll angle with wave length (λ/L = 1.5) can reach to 5.79° by contrast with 0.85° in calm water. Surfacing depth has a great influence on the changes of submarine trim during surfacing. For rolling motion in the transverse wave, maximum roll angle with depth length ratio (d/L = 1.2) can reach to 2.46 times as much as that with depth length ratio (d/L = 0.6).