Analysis Of Motion Interference Characteristics Of USV Chasing Mother Ship In Calm Water

The stern-slipway launch and retrieval system is one of the main methods for the launch and recovery of USV.When the USV is close to the devices in the stern of mother ship,it will be disturbed by the wake of mother ship,which will produce yaw force and moment,and it will bring difficulties to the motion control of the unmanned vehicle.This kind of motion interference process is a typical multi-body dynamics problem.In this paper,the model 4667-1 of 62 series planing hull is taken as the USV,and the model 5512-MS is taken as the mother ship.Based on self-developed CFD software,the motion interference characteristics of the USV in the process of approaching the capturing device of the mother ship in calm water are studied by using the multi-moving domain dynamic overset mesh method.Firstly,the resistance and attitude of the USV and the DTMB 5512 are simulated numerically,and the simulation results are compared with the experimental data to verify the reliability of the numerical method.Then,based on the detailed study of the mother ship’s wake,the motion interference characteristics of the USV in different positions in the mother ship’s wake at the same speed were numerically simulated.By comparing with the results in calm water,the influence of the mother ship’s wake at different positions on the motion of the USV was quantitatively analyzed.Finally,the multi-degree of freedom motion simulation is carried out for the motion process of the USV chasing the mother ship along different paths.By analyzing the changes of the resistance and attitude of the USV during the pursuit process,the motion interference characteristics in the longitudinal recovery process of the USV are studied.The results show that the propagation and distribution characteristics of the mother ship’s wake have a direct impact on the motion characteristics of the USV,and the wake gradually decreases in the outward propagation process.The separation flow around the stern dissipates faster,and the wave flow travels farther.Therefore,the far field is mainly affected by the wave flow.The near-field wake strongly interferes with the motion of the USV,which results in the drastic changes of its resistance and attitude in a short period of time.Diverging waves cause transverse interference to the USV,while transverse waves mainly cause longitudinal motion.When the USV is at the junction of shear wave and dispersive wave,its wake often interferes and fuses with the mother ship’s wake.At the same time,the wave surface at the wedge-shaped boundary of the wake is steep.At this time,the USV is most disturbed by the mother ship’s wave,so the USV’s sailing route in the recovery process should try to avoid this area.The research shows that the self-developed software HUST-SHIP can better simulate the dynamic disturbance characteristics of the USV in different wake areas,and the results are of great significance for the development of the control strategy and recovery device of the USV.