Study on the Effect of Upstream Small Cylinder on the Aerodynamic Performance of Airfoil

A passive flow control method, namely upstream small cylinder, was numerically investigated for vertical axis wind turbine. The small cylinder was installed in the front of the leading edge of the NACA 0018 airfoil. The effect of the cylinder on aerodynamic performance of the airfoil was studied by changing the diameter of the cylinder and the distance between the cylinder and the leading edge of the airfoil at Re=2×10⁶. The results showed that when the cylinder was placed in proper positions, the stall angle was effectively delayed (with maximum delay angle of 8°), the lift and tangential force coefficients were increased and the drag coefficients were reduced at large angles of attack. In addition, the cylinder with a relatively large diameter showed better control effect over a wider range of the distance.