Study On Aerodynamic Characteristics Of Flapping Wings Motion Mode And Geometric Feature

FWMAV(Flapping Wing Micro Aerial Vehicle)is a new type of MAV simulating the flight of insects or birds.Compared with fixed-wing micro aerial vehicle and rotary-wing micro aerial vehicle,it can overcome the aerodynamic limitation of small-scale and low Reynolds numbers and generate lift and thrust simultaneously to achieve the function of lifting,forward flying or hovering by only flapping wings.It also can change flight mode flexibility by adjusting flapping parameters,which makes it have nice maneuverability and high flight efficiency and more suitable for military mission.So it has great development and research value.Aerodynamic mechanism is the theoretical basis of designing and developing the FWMAV.Although there have been many studies on aerodynamic mechanism,it still has a long way to go.In this paper,insect is selected as biomimetic research object,using the computational fluid dynamics method to make a numerical study on aerodynamic characteristics of flapping wings motion mode and geometric feature and then verifying the numerical result by experiment.The main work and contributions in this paper are as follows:Firstly,the paper analyzed the differences of flapping wings motion mode and geometric feature between insects and then used a new computational fluid dynamics method,the lattice Boltzmann method,to establish the flapping wing numerical calculation model.The method was verified by calculation examples.Then,the paper systematically studied the variation of flapping wing motion mode on aerodynamic forces by increasing the degree of freedom of flapping wing sequentially.The results showed that the simple flap generated little periodic average lift;the symmetrical “eight” flapping wing motion mode both generated periodic average lift and thrust and the magnitude of lift and thrust were related to the tilt angle of the “eight”,raised the tilt angle,lift decreased and thrust increased and it could achieve different aerodynamic effects by adjusting tilt angle and torsional amplitude;the irregular “eight” flapping wing motion mode could increase the periodic average thrust but reduce the periodic average.Next,model wings having different shape but the same span and area and corrugation having different shape and amplitude are designed artificially,the paper further studied the effect of wing shape and corrugation on aerodynamics force in hovering.The results showed that the wing shape having more area outboard can generate more periodic average aerodynamics force but the corrugation has little effect on aerodynamics force.Finally,the single degree of freedom flapping device was used to verify numerical study's conclusion about the effect of wing shape on aerodynamics force,which showed the accuracy of numerical calculation.