Numerical Simulation Of Aerodynamic Characteristics Of Flapping Wing At Low Reynolds Number

Flapping wing flight is a unique flight mode of insects,birds and bats.It has some advantages,such as high mobility(hovering flight or even inverted flight),low flight noise,strong concealment and low energy consumption.Flapping wing flight technology has broad prospects in civil and military fields,and can create huge social and economic benefits.At this stage,people have a more in-depth study of flapping wing flight,and found some important flapping wing flight principles,but there are still some shortcomings,which need further in-depth study,further clarify the flapping wing flight mechanism,and then guide the design and manufacture of flapping wing aircraft.In this paper,the Bionic Flapping Wing is taken as the research object,and the numerical calculation method is used to study the influence of low Reynolds number(Re < 2000)flapping wing airfoil,frequency,phase difference,flight trajectory,airfoil flexibility and different flapping wing layout on the aerodynamic characteristics of flapping wing.It can not only improve the existing flapping wing flight theory,but also provide theoretical support for the design and manufacture of flapping wing aircraft.1.Firstly,the lift mechanism of flapping wing under different incoming flow conditions is studied,the flapping wing flow field model is established.And the finite volume method is used to solve the flow field of flapping wing,and the flow field structure is analyzed and summarized.The numerical results verify the lift mechanism of flapping wing found by predecessors.Further research on the lift mechanism shows that there is a certain interaction between the lift mechanisms.2.Secondly,the finite volume method is used to investigate the influence of the flapping wing motion parameters on the aerodynamic characteristics of the flapping wing.It is found that increasing the flapping wing frequency can increase the strength of the leading edge vortex,which can improve the adhesion of the leading edge vortex,and thus improve the aerodynamic characteristics of the flapping wing.The phase difference between the translational and rotational motions of the flapping wing will affect the effective angle of attack of the flapping wing and the lift and drag characteristics of the flapping wing.When the parameters of horizontal translational motion and rotational motion(amplitude,frequency,phase difference,angular velocity,etc.)are the same,the lift coefficient of flapping wing with horizontal straight trajectory is larger than that of elliptical trajectory and "?" trajectory.When the parameters of horizontal translational motion and rotational motion are the same,the lift characteristics of flapping wing with different axisymmetric trajectory are significantly different.3.Finally,the finite volume method is used to study the influence of the structural parameters on the aerodynamic characteristics of the flapping wing.The lift coefficient of goe464 airfoil is higher than that of elliptic airfoil,NACA0012 airfoil and rectangular airfoil.The influence of different thickness ratio of airfoil on the aerodynamic characteristics of flapping wing under different incoming flow conditions is studied.The influence of thickness ratio of flapping wing with and without incoming flow on the aerodynamic characteristics of flapping wing is different.The aerodynamic characteristics of flapping wing with different chord flexibility are studied,and the influence of chord flexibility deformation on the aerodynamic characteristics of flapping wing is found.It is found that under certain conditions,the aerodynamic characteristics of flapping wing with tandem arrangement are better than those of flapping wing with parallel arrangement.