Validated Unsteady Computational Fluid Dynamic Analysis of an Oscillating Bio-Inspired Airfoil

Abstract

An unsteady, two-dimensional numerical study was conducted to investigate the aerodynamic and flow characteristics of a bio-inspired corrugated airfoil oscillating at 2Hz with an amplitude of 10°. The upstream flow was set such that the chord Re = 14,000. The computational results were validated against experimental results from a 2D particle image velocimetry (PIV) experiment on the same airfoil geometry. Complex flow structures such as the formation and shedding of trailing edge vortices have been revealed to have significant impacts on the lift and drag characteristics of the airfoil in oscillating motion. The shed vortices provide a low pressure region on the top surface of the airfoil throughout the period of oscillation, thus increasing lift of the airfoil. In particular, vortices formed and shed from the rear-most corrugation appear to have the largest effect. The pitch-down motion produces a lower absolute peak lift as compared the pitch-up motion which may be explained by the disruption of the high pressure zone on the top surface of the airfoil by a vortex forming in the corrugations. This results in a relatively lower high pressure region on the advancing side as compared to the pitch-up motion. In addition to the lift calculations, drag calculations indicate that net thrust is being produced during the oscillations and more thrust is produced on the pitch-up than the pitch-down motion.