Stability Analysis Of Underwater High-speed Vehicle

Underwater high-speed vehicle achieves supercavity flow through high-speed motion,which greatly reduces the drag on the vehicle,greatly improves the speed,and improves the range,so as to achieve the goal of rapidly striking the target.At the same time,there are many disturbance factors in the complex multi-phase flow field.When the size of the cavity is larger than the vehicle,forming supercavitation,the vehicle body is completely exposed to gas,its wetted area is greatly reduced,most of the planing resistance,differential pressure lift and buoyancy disappear.Forces also become complex and highly nonlinear,often leading to yaw and loss of control.Based on the analysis of the dynamic characteristics of the underwater high-speed vehicle,this paper establishes the dynamics and kinematic model of the vehicle.The main research contents and conclusions are as follows:Firstly,a dynamic model suitable for the calculation of small unpowered underwater vehicle was established.The ballistic analysis program for the vehicle penetration and navigation was compiled.Compared with the literature,the reliability of the calculation program was verified.Secondly,under the non-disturbance conditions,the effects of the diameter of the cavitator,the length of the vehicle,the mass distribution of the vehicle and the total mass of the vehicle on the range and trajectory offset of the vehicle are studied.The study found that the use of proper cavitation diameter and a large total mass of the vehicle will significantly increase the range of the vehicle;the length of the vehicle will affect the range of the vehicle by affecting the stability of the vehicle;the centroid is more forward and the the inertia is greater,the better the stability of the body.Finally,give different pitching angular velocity for penetration,and calculate and analyze the motion stability of the vehicle.The initial pitching angular velocity increases,and the trajectory offset increases first and then decreases.Based on Savchenko's instability criterion,the shape of the vehicle with good stability is optimized by analyzing the calculation results.In the case of constant penetration speed,penetration angle,length,diameter and density of the vehicle,the stability andrange of the preferred vehicle are significantly improved with respect to the preceding vehicle.The work of this paper lays the foundation for the underwater vehicle shape design,ballistic calculation,stability research and control.