| The Passive-power Underwater Vehicle(PUV)relies on the interaction between its own gravity and water to achieve the purpose of diving and approaching the target without additional power supply.The program can well solve the shortcomings of current miniature PUV such as insufficient battery life,so that the PUV has extremely high concealment.This paper uses numerical simulation to study the kinematics and mechanics of the PUV’s free diving in detail,which has guiding significance for the design and path planning of the unpowered submersible in the future.This article has carried out the following research work:(1)It determines the parameters that affect the free diving state of the PUV as density ratio and eccentricity,and determines the overall research plan and route.Through the potential flow superposition theory,it is proved that the additional mass of the PUV only depends on the geometric parameters of the submarine;the additional mass and the additional moment of inertia of the PUV are obtained through conformal transformation.Introducing correction of gravitational moment caused by eccentricity and fluid additional to modify the rigid body dynamic equation,the dynamic equation of the PUV free diving is obtained.(2)It divides the computational domain reasonably.Revising the numerical model based on the Reynolds time-average method,using the finite difference method to simulate the free falling of the submarine miniature model experiment in the known literature.The simulation shows that the modified numerical model is correct.(3)By changing the two parameters of density ratio and eccentricity,the modified numerical model is used to simulate the free diving of the submarine.Through the statistics of the motion state,a total of five different results are obtained,including Tumbling,Chaotic,Gliding Dominated,Gliding,Fluttering.The kinematics in various motion states and the induced force and induced torque obtained by solving the modified dynamic equation in various motion states are analyzed in detail.(4)From the aspect of the miniature model of PUV wake vortex,the mechanics of the PUV diving is analyzed,the mechanism that causes the submersible’s diving instability is explained,and the distribution and changes of the wake vortex in each cycle under each motion mode are analyzed.It also explains the influence of the time-varying wake vortex distribution on the vortex induced force and induced torque. |
