Research On The Motion Performance And The Water Entry Of The Free Fall Of The Disk Type Nderwater Glider

The disk type underwater glider is a new type of underwater gliders whose shape is obviously different from existed traditional underwater gliders,and its shape is an axisymmetric disk.It does not require the long-distance rotary motion,and the movement direction can be changed by adjusting the internal sliders,so it is more maneuverable and more suitable for motorized movement in the small water environment.This paper takes the prototype of the disk type underwater glider designed and developed by our research group as the research object.First of all,based on the steady motion equation of glider and using CFD technology,this paper establishes the shape design analysis method of the disk type underwater glider,and then analyzes the influence of the diversion edge and the gilder height on its hydrodynamics and motion performance.It is found that the gliding distance in the horizontal direction corresponding to the unit height in the vertical direction is increased by the diversion edge,while the sliding speed in the horizontal direction is decreased.The decrease of the gilder height increases the sliding speed in the horizontal direction,while it has no influence on the gliding distance in the horizontal direction which corresponds to the unit height in the vertical direction.Then,considering the influence of the internal slider motion of the disk type underwater glider,this paper regards the glider as a multi-mass system and establishes a nonlinear dynamic model.Based on the axisymmetric characteristics of the disk type underwater glider,a special viscous hydrodynamic calculation method is proposed to satisfy its omnidirectional maneuverability.The typical motion of the disk type underwater glider(including horizontal sawtooth movement,vertical sawtooth movement and omnidirectional motion)is simulated.The simulation results show that the dynamic model established in this paper is feasible and the disk type underwater glider has a good maneuverability.Finally,based on the finite volume method,the problem of the water entry of the free fall of the disk type underwater glider in still water is studied.In order to illustrate the effectiveness of the numerical simulation method,the process of the small sphere entering the water are simulated.The numerical simulation results agree well with the experimental results,which indicates that the numerical simulation method is credible and can be used to study the problem of the water entry of the disk type underwater glider.Based on the validated numerical model,this paper discusses the influence of the initial water entry velocity and angle on the attitude,trajectory and the impact load of the glider in the process of entering the water.