Effects of Reynolds Number and Protuberance Amplitude on Twin-Protuberance Airfoil Performance

Abstract

A stall occurs in the flow around an airfoil when the angle of attack reaches a critical value, leading to a dramatic drop in airfoil performance. Recently, a passive leading-edge protuberance control method, inspired by the fin of a humpback whale, has demonstrated obvious advantages in improving airfoil stall. Hence, this study experimentally and numerically investigates the aerodynamic characteristics of an airfoil with twin protuberances at the leading edge. First, the aerodynamic characteristics were investigated for six Reynolds numbers via wind-tunnel experiments, obtaining the hysteresis caused by the test sequence. Then, numerical simulations were performed using a transition shear stress transport turbulence model, and the numerical accuracy was verified. Finally, the influence of structural parameters on stall behavior was revealed by changing the amplitude of the protuberance. The results indicate that the twin-protuberance airfoil produces step-by-step and one-side stall phenomena. The influence of vortices on the movement of separation bubbles on the lower surface is presented. The critical angle of attack for stall increases with increasing Reynolds number; its value for deep stall increases by more than 2 deg. As the protuberance amplitude is reduced, the influence on the airfoil flow is weakened, and the first stall angle increases.