Effects of Reynolds number and pitching amplitude of oscillation on the aerodynamics of a flapping airfoil

Abstract

Computational fluid dynamics (CFD) simulations of an airfoil performing a figure-eight-like kinematics is conducted in low Reynolds number (LRN) flow regime. Finite volume method (FVM) is used to discretize the governing two-dimensional (2-D) Navier-Stokes (N-S) equations. The flow field and vortical patterns around the airfoil are examined in detail, and the effects of amplitude of pitching oscillation and Reynolds number (Re) on the aerodynamic characteristics of the model are explored. Lift and drag coefficients, as well as their ratio as the performance benchmark, are calculated and compared. The results show that both Re and amplitude of pitching oscillation are important parameters in the LRN flow. They influence the lift and drag coefficients by altering the generated vortical patterns and varying the peaks of the force coefficients. The results also show that the aerodynamic efficiency of the present figure-eight motion is much higher than the efficiency of the conventional flapping kinematics used in the literature.