Numerical simulations of submarine self-propulsion flows near the free surface

Abstract

Submarine needs to complete more tasks near the free-surface area in modern war. When sailing near the free surface, the self-propelled characteristics of the submarine and its nearby flow field will be affected by the free surface. This paper presents the research on the self-propulsion submarine near the free surface with computational fluid dynamics (CFD) method. We take the generic Joubert BB2 submarine and Marine 7371R propeller models as the research objects. The RANS method and SST k-ω turbulence model are selected to solve the turbulent flows. The volume of fluid (VOF) method is used to capture the free surface. Grid convergence study is performed based on three sets of grids with different resolution. Numerical simulations are performed under the self-propulsion cases with different submergence depths and velocities. The proportional integral (PI) controller method is proposed to obtain the self-propulsion point. The results are more accurate compared with the traditional one. It is found that with the decrease of the submergence depths, the rotating speed of the self-propelled point and the corresponding thrust increase. The study also explores the free surface effect on flow field characteristics, wave-making characteristics and vortex structures. The scientific findings provide some useful results for the self-propulsion submarines near the free surface and support the further research in the future.