The effect of vortex induced vibrating cylinders on airfoil aerodynamics

Two-dimensional fluid-structure coupling dynamic models of single- and double-cylinder with airfoil are established using fluid-structures dynamics methods. The accuracy of the airfoil and vortex-induced vibration simulation models is verified by comparing them with available experimental data. Coupled simulations are used to study the vortex-induced vibration of two cylinders under uniform incoming flow, and the influence of two cylinders at different positions of the airfoil leading edge on their aerodynamic forces. Vorticity and streamline diagrams provide evidence of the effects of single cylinder and double cylinders on the airfoil when placed at different angles of attack. The vibration response of the cylinder is also observed. The results show that at high angles of attack the flow separation of the airfoil can be effectively controlled by positioning small cylinders in the proximity of the airfoil's leading edge. A small oscillating cylinder can contribute to control the flow around the airfoil, better than fixed cylinder. Indeed, when the airfoil is within stall condition, a single vibrating cylinder can control flow separation and improve airfoil lift-to-drag ratio, better than when no cylinder or double cylinders are considered. For increasing angle of attack post stall condition, the ability of a single oscillating cylinder to control the flow around airfoils decreases gradually, while the one of double cylinders increases.