| Underwater gliders rely on hydrodynamic components acting on the wings to complete a series of basic movements such as up,down,and turn.Low energy consumption is one of the main characteristics of underwater gliders.Flapping wing propulsion is a bionic drive method which imitates turtle and humpback whales to generate forward thrust.It has characteristics of high maneuverability and propulsive efficiency.An underwater glider that combines gliding and flapping can better adapt to diversified mission requirements and complex ocean environment,so it has a huge potential application prospect in Marine military and underwater rescue.In this paper,a design scheme of the soft wing which suitable for both gliding mode and flapping modes is proposed.The hydrodynamic simulation of gliding motion and flapping motion is studied,and the tank experiment is completed.The main research contents and achievements are as follows:Firstly,focusing on the gliding mode of the soft wing,the hydrodynamic simulation of the gliding motion of the underwater glider with passive deformation of the soft wing is completed.From the perspective of the gliding economy,stability and cost,the influence of different cross-section shapes,declination angle and outer contour of the soft wing on gliding hydrodynamic performance are discussed.The simulation results are compared with the hydrodynamic performance of rigid flat wings,and the advantages and application range of soft wings are given.Based on the simulation results and some characteristics of underwater creatures with flapping-wing movement,a design scheme of the soft flapping-wing is presented,the mathematical model of flapping-wing movement is constructed approximately,the overall layout of the glider that combined gliding and flapping is formed.Comparing the soft flapping-wing with the rigid flat-wing and the common multi-joint flexible flapping-wing,the innovative points and advantages of the soft flapping-wing in this paper is given.Secondly,focusing on the flapping mode of the soft wing,the instantaneous flow field simulation of underwater flapping-wing motion is completed.The variations of vorticity field during the flapping-wing process are given,and the corresponding relationship between trailing edge vortex and thrust force of flapping-wing is expounded.The effects of different working conditions and flapping parameters on the motion performance of the flapping-wing are summarized.The hydrodynamic coefficients and kinematic parameters of the underwater glider in flapping-wing mode are obtained.The results show that,within a given parameter range,the maximum propulsion efficiency of the software flapping-wing obtained by simulation solution in this study is about 52.3%,and the linear propulsion speed of the underwater glider with flapping-wings is about 0.6 m/s.Finally,the thrust measurement experiment of the flapping-wing prototype and the test of flapping-wing motion of underwater glider that combined gliding and flapping is completed.The effects of different flapping-wing parameters on the propulsion force are measured experimentally,which further verifies the accuracy of the simulation analysis.The experimental results also show that under the given parameters,the linear propulsion speed of the glider with soft flapping-wings is about 0.528 m/s,and the whole turning time is about 55 s,which prove the characteristic of high maneuverability. |
