Research On Hydrodynamic Characteristics For Twin Tail Semi-Submerged Unmanned Vehicle Moving Near The Free-Surface

Unmanned vehicles are widely used in civil,military and commercial for its great maneuverability,stealth and reliability.According to the scope of work activities of unmanned vehicles,it can be divided into unmanned surface vehicles and underwater unmanned vehicles,while underwater unmanned vehicles are also known as autonomous underwater vehicles or unmanned submersibles.Since the first submersible was introduced in Switzerland in 1932,the development of miniature submersible has shown a thriving trend.There has evolved out kinds of submersibles with various shapes?sizes and wide range of functions up to now.Submersibles can achieve autonomous navigation and remote operation navigation.People also benefit from promoting the development of submersibles.The interaction between the free surface and the submersible is significant when the submersible is about to operate near surface for actual work requirements or deployment and recovery,bow-bury phenomenon is evident.Therefore,it is of great significance to study the coupling induction between the free surface and the submersible.In this paper,the FVM based Star-CCM+ software is used to investigate the hydrodynamic performance of Afterbody-1,a body-of-revolution model,to obtain a preliminary understanding of the interaction mechanism between the body-of-revolution model and the free surface.In this paper,a new ship type twin tail semi-submersible unmanned vehicle is proposed innovatively based on the features of unmanned surface vehicle and submersibles.The application of the unmanned craft mentioned above is the river and offshore survey and mapping.Its navigation space is limited in the near surface,only part of hull body can be seen above the water when sailing.On the one hand,it can avoid the waves,on the other hand,it won't be restricted by the depth of the water,and can greatly improve navigation safety.By comparing the resistance values and the two degrees of freedom including heave and trim of four different models under the same operating condition,the optimal performance model was found and the influence of the attachment to the hull was analyzed.Matching design of ducted propeller for unmanned vehicle was based on relevant design manuals,and then self-propulsion point can be obtained under a certain inflow velocity.There is a major advantage of the twin tail structure that it can achieve steering and turning circle by changing the propeller rotating rate.Finally,two different forces are applied to the twin tail to study the motion response of twin tail semi-submerged unmanned vehicle.