Numerical simulation on the effects of water holes on the hydrodynamic forces and separation of the underwater vehicle at high angles of attack

In emergency situations, underwater vehicles adopt emergency ascent measures by discharging water through water hole jets. Previous studies have mainly focused on the effects of water holes on the overall ascent kinematics of underwater vehicles, whereas the effects of water hole jets on the hydrodynamic performance and flow separation of underwater vehicles during emergency ascent at a large angle of attack have not been sufficiently investigated. In this study, the effects of water hole jets on the hydrodynamic performance and flow separation of an underwater vehicle at high angles of attack are investigated using detached eddy simulation. Regarding hydrodynamic performance, both the drag coefficient and lift coefficient increase with jet velocity, with the most significant variations occurring near the water holes. Concerning flow separation, the jets have a minor effect on flow separation in the vicinity of the water holes. Based on the numerical results and using the dimensionless longitudinal development time, the separation line model is extended to accurately predict the flow separation angle of the underwater vehicle at a high angle of attack.