Aerodynamic research of flapping/gliding flight in low reynolds number flow

This paper aims to research the aerodynamic characteristics of flapping/ gliding flight of birdlike micro flapping wing. Birds in nature always fly in the way of combining flapping and gliding flight together to save physical energy. The weight of Flapping-wing Micro Air Vehicle (FMAV) is strictly limited by its small size, hence the energy is limited. Inspirited by the natural flyer, if the FMAV flies combining flapping and gliding flight together, it can save energy and fly much longer. This paper uses the numerical simulation to research the aerodynamics of flapping/gliding flight. The flow over the micro flapping wing is low speed and viscous. Reynolds number is about the range of 5∼10e4. Numerical method is solving the Reynolds Averaged Navier-Stokes (RANS) equations. Preconditioning method is used for the low speed flow over FMAV. Multigrid method is used to accelerate the convergence. Spalart-Allmaras turbulent model is coupled into the RANS equations. Three principles for wing suitable to flapping/gliding combining flight are proposed. The results show that thin airfoils with medium camber can get good performance both in flapping and gliding flight. They generate bigger lift both in flapping and gliding ; have a high lift/ drag ratio and a relative small drag or big thrust.