Aerodynamic Characteristics of Airfoils Equipped With Gurney Flaps and Vortex Generators for the Entire Range of Pitch Angles

ABSTRACT An experimental study of NACA0021 airfoil equipped with vortex generators (VGs) and Gurney flaps (GFs) was conducted to assess the effects of these devices on the aerodynamic airfoil performance, the information that is necessary for studying the self‐starting characteristics of vertical axis wind turbines (VAWTs). This is particularly important given current efforts to enhance the efficiency and lifetime of VAWTs. The pressure distribution on the airfoil was assessed for the entire angle of attack ( AoA ) range (i.e., 0° ≤ AoA < 360°). Four airfoil configurations were studied, i.e., (a) the baseline airfoil, (b) the airfoil with VGs, (c) the airfoil with a GF with a height of 0.014 chord ( c ) lengths, and (d) the airfoil with a GF of height 0.025 c . VGs yield a 33.3% increase in the AoA at which the flow reattaches and 16.3% increase in the maximum lift force coefficient c L . Configurations equipped with GFs exhibit 27.9% increase in the maximum c L and a concurrent increase in the lift‐to‐drag ratio.