Direct Simulation Of Maneuver Of The Underwater Vehicle Based On Overset Grid

Maneuverability is one of the most important hydrodynamic performances for underwater vehicles.Accurately predicting its motion characteristics in maneuvering motion is very important for the safety and design.In the initial design stage,the traditional design method for the submarine maneuvering motion prediction is based on the simplified mathematical model,which is effective and rapid,but results are dependent on the validity and the accuracy of the mathematical model deeply,and the detailed analysis of the flow field is impossible.With the development of Computational Fluid Dynamics(CFD)technology and the rising of parallel computing,the direct simulation,which couples the six-degree-of-freedom motion equation of ships with flow field calculations,provides another kind of possibility.In this paper,DRAPA SUBOFF submarine was studied and the STAR CCM + commercial software package was used to achieve the entire maneuver phase of horizontal overshoot and the turning movement simulation.In the simulation,the DFBI module was used to couple the flow field calculation with the 6-DOF motion of the ship.Overset grid technology was used to deal with the complex relative motion between the appendage and the hull.The rudder was controlled by the written function,the changing of its trajectory and attitude during maneuvering was predicted,and the flow field information was captured.Firstly,the numerical simulation of the SUBOFF towing motion was carried out.Results of resistance prediction and flow field details were in good agreement with experimental results,which verified the accuracy of the numerical method.Secondly,in SUBOFF’s self-propulsion prediction,three cases were used,and simulation results were compared with those of other researchers.In the following direct simulation,the self-propulsion simulation was used as its the initial stage,in which the propeller was replaced by the body force model.The motion trajectory,the heading angle,the yaw velocity,the drift angle,the time history curve of the speed dropping,the roll and pitch were analyzed in the horizontal overshoot motion.Vortices in motion were captured too.Finally based on the above work,the detailed analysis of the similarities and differences between the full complement SUBOFF matched with X rudder and the rudder was performed under different rudder angles in the turning motion simulation.It was found that the X rudder had significant advantages over the horizontal rudder in terms of horizontal overshoot maneuver.Forces and moments in the stabilization phase and the flow changes along the hull were analyzed at the same time.