Fluid-structure coupling research for micro flapping-wing

A method of fluid-structure coupling research for micro flapping wing is presented in this paper. The wings of FMAV (Flapping-wing Micro Air Vehicle) always are light weight and elastic structure. The wings will deform by the pressure of aerodynamic force generated by the flapping motion. The fluid-structure coupling problem is important to study the true state of flapping wing. The aerodynamic forces are obtained by solving the RANS (Reynolds-Averaged Navier- Stokes) equations. The preconditioning method is used to solve the convergence problem in low speed. The chimera grids method is used to simulate the flapping wing. The stiffness matrix used in computational structure deformation is tested by experiment in high precision. An experiment method based on linear fitting is developed to test the stiffness matrix of flexible wing. The distributing surface forces are translated onto the structure nodes. The motion governing equations are simplified for preliminary research. Inertial force and damping force are ignored because the flapping frequency is far less than the natural frequency. The method is the basic trial to study the effect of elastic deformation of flexible flapping wing to the aerodynamic characteristics. The results show that the deformation of flexible wing will decrease the fluctuation of aerodynamic forces generated by wings' flapping motion. The deformation is generated mainly by lift, and the average lift will decrease a little but the thrust will increase for the deformation manner of relatively rigid leading edge. Therefore proper flexible wing will increase the thrust and make the air vehicle more stable.