Aerodynamic Analysis And Biomimetic Application Of Dragonfly Wing Leading Edge Microstructure

In today’s society,energy shortage is an important problem facing the development of all countries.Efficient utilization of renewable energy has gradually become a hot topic for scholars at home and abroad.Dragonfly is a kind of organism with high flying ability,and its special wing structure provides inspiration for exploring the aerodynamic theory of wing in the field of bionics.In this paper,the aerodynamic characteristics of dragonfly wing leading edge pulse microstructures are studied.Three kinds of leading edge microstructures are designed and applied to the leading edge of subwing wing and propeller blade.The aerodynamic performance of increasing fan bottom microstructures and reducing drag of long flat bottom microstructures is verified by simulation combined with experiments.Scanning electron microscopy was used to observe the leading edge pulse microstructure of dragonfly wings.The models of leading edge pulse and fan-bottom microstructure were established,and the long flat bottom microstructure and short flat bottom microstructure were obtained by changing the microstructure characteristics.Three single arrays of front edge microstructures were obtained by arrays of three microstructures respectively.The leading edge pulse and microstructure were combined and connected on the leading edge of the wing to get a double row of leading edge pulse microstructure wings.The simulation scheme of wings in gliding flight is designed,and the lift drag coefficients of single and double wings are simulated.After comparing the lift drag performance of the two wings,the wings with a single row of leading edge microstructure were selected as the research object to analyze the influence of the microstructure on the wing airflow.It was found that the fan-shaped bottom structure could accelerate the airflow flow,strengthen the leading edge vortex intensity,improve the kinetic energy of the boundary layer top flow,and provide stronger suction for the upper wing surface.The long flat bottom structure eases the Angle of attack,makes the low-speed air flow to the airfoil flow closer to the wall more stably,reduces the turbulence degree of the vortex behind the wing,and reduces the pressure difference resistance between the front and back of the wing.In order to adapt the microstructure to a wider range of wings,the two leading edge structures with the best aerodynamic performance were amplified at different multiples,and the optimal amplification of the two structures was determined by the results of wing lift resistance.According to the optimal structure size of the amplified leading edge,a propeller blade model of corresponding size was established.The two structures were respectively arrayed on the leading edge of the propeller blade,and the pull and reaction moment values of the propeller blade were obtained by rotating simulation with the help of sliding grid technology.It was found that the fan-shaped base front structure could increase the pull of the propeller,while the long flat base front could reduce the reaction moment of the propeller.By analyzing the rotating flow field of the propeller blade,it is known that the airflow passing through the leading edge structure of the front blade affects the incoming flow velocity of the rear blade,and then changes the pressure of the upper and lower airfoil and leading edge of the blade,thus changing the aerodynamic performance of the propeller.Finally,a wind tunnel test system and a rotating test system were built to measure the lift resistance of the wings and the pull and reaction torque of the propeller at a constant speed under glide conditions.The experimental measurements and simulation values were compared to verify the effectiveness of the simulation and further define the aerodynamic effects of the leading edge structure.