New Flow Control Optimal Design Method of Flapping Wing Coupled with a Prepositive Elliptical Wing

Abstract

A flapping-wing flow control method based on a prepositive elliptical wing is proposed in this study. A tiny elliptical wing is designed at a specific position around the leading edge of the flapping wing to suppress and improve flow separation by the airfoil and achieve the purpose of increasing lift and reducing drag. Furthermore, the particle swarm optimization algorithm is used to optimize the aerodynamic design of the prepositive elliptical wing–flapping wing composite configuration under attached flow and separated flow. The long axis length, short axis length, deflection angle, and positional relationship with the main wing of the prepositive wing are taken as the design variables, and the maximum time-averaged lift-to-drag ratio in a flapping cycle is taken as the optimization objective to obtain the optimal configuration under attached flow and separated flow. The simulation and optimization results show that the increment of the time-averaged lift-to-drag ratio of the prepositive elliptical wing–flapping wing optimal configuration under attached flow is 1.2 times that of the original airfoil, while the increment of the time-averaged lift-to-drag ratio of the optimal configuration under separated flow is approximately 0.5, and the prepositive wing completely inhibits the separation of the flow on the top surface of the flapping wing. In addition, the influence of the parameters is analyzed, and a general design for the prepositive elliptical wing–flapping wing configuration is given.