Propulsion Design And Dynamic Analysis Of Flapping-foil Underwater Vehicle

At present,most of the underwater vehicles adopt the traditional propeller propulsion.However,with the development of the utilization to the ocean and the complexity of the tasks to the marine survey and engineering,the traditional way is difficult to meet the need of diverse tasks.The research of flapping foil propulsion technology is an effective way to improve the performance of underwater vehicles.This thesis analyzed the hydrodynamic characteristics of the flapping foil by using the method of computational fluid dynamics.Then,the flapping-foil & gliding underwater vehicle and its flapping foil propulsion were designed.Dynamic analysis of the vehicle was also completed here.The main research results of this thesis are summarized as follows:1.By using the method of computational fluid dynamics,a preliminary study on the flow field structure and hydrodynamic characteristics of the flapping foil was done.The results showed that thrust force increased but efficiency reduced with the flapping frequency increasing.And flapping foil with asymmetric motion could produce the nonzero mean lift which allowed the resultant force to be rotated out of the moving direction of underwater vehicle,thus maneuvering the vehicle.2.A novel manipulator of two degrees of freedom flapping-foil propulsion was designed based on a spherical parallel mechanism.The kinematic equation and dynamic equation were established.Through the kinematic and dynamic analysis of the mechanism,the fully decoupling characteristic,which made it easier to be analyzed and develop the control system,was proved.What's more,it would be more suitable for practical engineering applications.The results of the variation of the driving velocity and driving force provided reference for the selection of driving motors.3.The forces and moments on the flapping-foil & gliding underwater vehicle,especially the hydrodynamics,were analyzed.Then a dynamic model of it was constructed utilizing Newton-Euler equations.By using the MATLAB software,the gliding mode with buoyancy driven and the fixed-depth navigation mode with flapping foil driven were simulated.When the frequency of the flapping foil was 0.5Hz,the velocity of the vehicle was approximately 0.85~0.92m/s.The changing characteristics of attack angle,attitude angle and depth were also obtained.These could provide references for designing flapping-foil & gliding underwater vehicles.