Simulation And Analyzation On Unsteady Aerodynamic Of Flapping Wing

Flapping wing flight is a common used flight mode of nature's flying creatures.Compared to the fixed-wing and rotary-wing flight mode,flapping-wing flight can generate lift and thrust simultaneously just relying on the wing's flapping motion,and it has the unique advantages of high flight efficiency,high maneuverability and compact structure.Flapping wing flow field is a low Reynolds number unsteady viscous flow,so the traditional steady aerodynamics for fixed-wing or rotary-wing can no longer be used directly.Aimed to reveal flapping-wing flight unsteady aerodynamic theory,the fundamental issues of flapping wing flight,airfoil aerodynamic characteristics and flapping-wing mechanism are studied systematically inthis thesis.The thesis discusses the rule of flapping-wing flight,analyzes and refines the form and mechanism of both birds and insects,and summarizes the mechanism of effect of the flapping wing flight on the aerodynamic force.In order to simulate the unsteady flow field of the flapping wing,simple harmonic motions are used to approximate the flapping-wing motion.By solving the change process of two-dimensional unsteady aerodynamic force and combiningthe theory of Theodorsen formula of unsteady aerodynamic force,the CFD calculation results are compared with the Theodorsen theoretical calculation results.Both two methods are verified to be effective on the unsteady aerodynamic force calculation.In order to find out the high lift mechanism of birds flapping wing,the unsteady aerodynamic force of the flapping wing which is under the condition of large Angle of attack and composite motion was calculated by using the CFD method.Based on thenumerical solution of several different shape airfoils' flapping wing flow fields,the airfoil aerodynamic characteristic curve is established,the airfoil flow pressure cloud picture is plotted,and the effect ofthe airfoil geometry and airfoil thickness on aerodynamic performance are analyzed.Based on the numerical methods,the flow fields of different motion parameterssuch asflap frequency,flight speed,plunge amplitude are calculated in detail for purpose of showing the influent of these motion parameters on flapping-wingaerodynamic characteristic.