Aerodynamic Analysis And Optimization Desigh Of Dragonfly-like Airfoil At Low Reynolds Number

Dragonfly wings have a complicated corrugation structure,which is significantly different from traditional streamlined wings.A large number of studies have studied the aerodynamic performance of the dragonfly’s corrugated airfoil from the perspective of bionics and applied it to the development of the dragonfly-like engineering airfoil as one of the methods to optimize the aerodynamic layout of the micro flapping-wing aircraft.Based on the principles of bionics and computational fluid dynamics,this paper conducts in-depth aerodynamic analysis and further optimization of the dragonfly-like engineering airfoil.Firstly,this article analyzes the structure of dragonfly wings,the laws of flapping wing motion and several common flying methods and explains several unsteady mechanisms by which dragonflies obtain high lift.Secondly,based on the existing literature research and combined with the numerical extraction software,the two-dimensional corrugated airfoils at different cross-sections of the dragonfly wing are established;based on the numerical simulation software FLUENT,the key aerodynamic parameters of the airfoil,and its static pressure and velocity distribution under the condition of low Reynolds number are calculated respectively by using the computational fluid dynamics method.The influence of the leading-edge orientation and the fold structure on the aerodynamic performance of the corrugated airfoil are then discussed.The results show that the leading-edge orientation and corrugation structure have a direct impact on the aerodynamic efficiency of the airfoil.When designing a three-dimensional wing,the corrugations of the dragonfly wings at different positions can be taken as a refer to make a more reasonable aerodynamic layout.At the same time,in the two motion states of gliding and flapping,this article explores respectively the influence of the two optimization methods of adjusting the corrugation amplitude and the additional camber on the aerodynamic performance of the airfoil,explores the further improvement by combining these two methods.The results show that in the process of gliding,the single adjustment of the corrugation amplitude or the additional camber has certain limitations in improving the aerodynamic performance of the airfoil.However,the combination of these two optimization methods can significantly increase the lift coefficient of the airfoil while reducing the drag coefficient,which proves to be an effective solution to achieve overall aerodynamic optimization of the corrugated airfoil;in flapping wing motion,the aerodynamic performance of the airfoil is affected by a variety of motion parameters which make the motion process more complicated,but the comprehensive optimization method can still effectively improve the aerodynamic characteristics of the airfoil during the flapping process.