2-way Fluid Structure Interaction Of Unsteady Aerodynamics Of Micro Flexible Flapping-wing

Flapping-wing flight has become more and more concerned because of its excellent flight performance and excellent maneuverability.Researchers have found that the flapping wing has a significant effect on the aerodynamic characteristics of the flexible structure.Therefore,it is very meaningful to control the flapping wing to produce proper deformation to obtain reasonable aerodynamic performance.As the wing flaps through the air,it is subjected to both aerodynamic force acting on the surface of the wing and inertial force due to the acceleration or deceleration of the wing's mass.The interaction between these inertial–elastic and aerodynamic forces resulted in wing deformation,which can influence the structure of flow field around the wing.Therefore,both values and distribution of pressure on the surface would change.In this paper,the fluid-solid coupling effect of flexible flapping-wing is analyzed by solving the continuous incompressible N-S equation and structural dynamics equation.The pressure gradient were calculated by using the immersion boundary method.The deformation of the structure was described by the finite element analysis,and the speed and the displacement was solved step by step.A decoupled control equation and a structural governing equation for a decoupled flow field based on a strongly coupled method are established.In this paper,open source CFD library based on OpenFOAM software is used to realize the secondary development and compilation of the solver of fluid-structure coupling algorithm.The structural model and the motion model of the flexible flapping wing are established,and the adaptive Cartesian grid is adopted to divide the model.The unsteady numerical simulation of the two-way fluid-structure interaction of the flexible flapping-wing model is carried out.The aerodynamic response and the structural deformation of the flapping-wing are analyzed at different movement moments.The influence of flapper thickness,flapping frequency,flapping plane angle and forward flight speed on the aerodynamic characteristics of the flexible flapping wing is numerically analyzed,which provides a theoretical basis for the design of the flexible flapping wing.The accuracy of the numerical simulation is verified by the experimental data.The results show that the aerodynamic response of the flexible flapping wing is closely related to the movement time and the structural deformation.In the reasonable range,the thinner airfoil will have greater flexibility effect;to improve the flutter frequency and increase the flapping plane angle will make the flapping wing get more lift and thrust;the faster the forward speed,the need to produce more large lift and thrust to maintain flight stability.