Research on aerodynamic-structural coupling of flexible flapping wings

Due to the coupling between large prescribed motions and flexible deformation, classical dynamics theory cannot be applied to a flapping wing's aeroelastic studies. In this paper, a dynamic aerodynamic-structural coupling computational framework is developed which is able to simulate the aerodynamic-structural coupling characteristics of a flapping wing. First of all, the periodic aerodynamic load of the flapping wing is obtained by a computational fluid dynamics (CFD) solver; then a computational structure dynamics (CSD) solver is used to get the periodic structural deformation as well as the periodic shape of the flapping wing. Repeat the procedure until structural deformation is converged. The flapping wing's unsteady aerodynamic characteristics are obtained by solving the Reynolds average Navier-Stokes equations. Structural dynamic equations capable of describing the flapping wing's movement are derived by use of the Hamilton principle, and then they are discretized through the finite element method. The discrete forms of the dynamic structural equations are then reduced to a series of easy-to-solve second order differential equations through modal analysis. Computational results show good agreement with experimental results, which proves that the proposed method is valid and suitable for simulation of a flexible flapping wing. Both rigid and flexible wing results of flow field details are further presented to demonstrate the effects of wing flexibility on aerodynamic performance.