Two-Dimensional Low-Reynolds Number Wind Tunnel Results for Airfoil NACA 0018

The two-dimensional characteristics of airfoil NACA 0018 have been measured for Reynolds numbers between 0.15×10⁶ and 1.0×10⁶ to establish the lift, drag and moment curves that serve as input to performance calculations of vertical axis wind turbines. At the lower surface laminar separation occurs at low to medium angles of attack, which is of significant influence on the characteristics and the radiated noise. For the situation with a lower surface laminar separation bubble, span wise wake rake traverse measurements showed an irregular three-dimensional pattern. Noise reduction could be achieved with zigzag tape at the 70% to 80% lower surface chord station. Significant post-stall hysteresis loops occurred showing a high loss in lift.