Design And Research Of Fully Morphing Flexible Flapping Wing Underwater Vehicles

Compared with conventional underwater vehicle,bionic underwater vehicles with flapping foil propulsion can obtain higher swimming efficiency and strong maneuverability in different swimming conditions.Thus it quickly becomes the frontier and hot topic of bionic underwater research.Fully flexible flapping wing can achieve higher efficiency,mobility and wider use among all the bionic underwater vehicles.However fewer domestic and foreign research were done.The complex flow mechanism and morphing mechanism are the most important factors to restrict the rapid development of the fully flexible flapping wing propulsion underwater vehicles.In this paper,the analysis and experimental study on the flow mechanism of the fully flexible flapping wing propulsion underwater vehicle are presented,including numerical method of unsteady flow field for large flexible flapping wings,simulations of nonlinear structure dynamics for flexible wings,study of fluid-structure interactions and propulsion mechanism,experimental prototype matching and testing.A computational model of fully flexible airfoil is proposed to realize the parameterization of airfoil flexibility.Numerical simulation of four basic morphing mechanism including steady morphing,rigid morphing,active flexible morphing and passive flexible morphing are performed to study the propulsion characteristics and the propulsion efficiency based on different morphing parameters and flexible conditions The effects of morphing and flexibility on the steady and unsteady flow field are discussed.A novel shell element suitable for large rotation and small strain is deduced based on the theory of composite laminates,which solves the nonlinear and geometric nonlinear problems of the flexible wings for their physiological structure and flutter motion.A dynamic analysis method of nonlinear flexible flapping wing based on co-rotational method is established,and its reliability is verified by statics,dynamics and modal analysis.The morphing structure of flexible wings was designed by finite element simulation and in-plane tensile and normal bearing tests.A novel fluid-structure interaction method was proposed especially for highly flexible structure.A high precision coupled cross-section interpolation algorithm is proposed to deal with the displacement interpolation problem of various large deformation and complex shape structures.The reliability of the fluid-structure interaction method is verified by examples of AGARD445.6 wing flutter model and Zimmerman-shaped micro-aircraft model.In this paper,a flexible flapping law is proposed base on the deduction of spanwise and chordwise flexibility.The mechanical properties of bionic underwater vehicles with flapping foil propulsion are analyzed by studying active flexible and passive flexible states.The test model of the underwater vehicle is designed and fabricated.The details of morphing structure,driving mechanism and body are designed to realize active flexibility and control of flexible flapping wing.A set of test platforms for the measurement of hydrodynamic performance of flexible pendulum was proposed.The experimental analysis of dynamic characteristics of the flexible pendulum with different motion parameters(frequency and angle of attack)was carried out,and the simulation results were confirmed.Then,the dynamic behavior of the underwater vehicle with upper and lower submerged motion of the underwater vehicle is analyzed,and the relationship between the flutter frequency and the swimming velocity is analyzed.Research provides some reference for future research.