Experimental study of stall in an airfoil with forced airflow provided by an integrated cross-flow fan

The objective of this article is to experimentally determine the stall characteristics of the FanWing airfoil. The experiments have been performed at various angles of attack, tip speed ratios, Reynolds numbers, and flap deflection angles. The experiments showed that the lift coefficient and stall angle of attack of the airfoil (value of angle of attack at which the lift-to-drag ratio is maximum) increase and its drag coefficient decreases with the tip speed ratio; however, its stall angle of attack decreases with the Reynolds number. Thus, high Reynolds number flows over this airfoil are more prone to separation and stall, and therefore, the tip speed ratio must be increased by enhancing the rotational speed or the angle of attack must be reduced to avoid stall and separation. It was perceived that the lift coefficient curve gives the maximum value at 40 degrees < alpha < 50 degrees (alpha is the angle of attack) interval, depending on the tip speed ratio and the Reynolds number. Experiments revealed that the airfoil lift coefficient increases significantly with the flap deflection angle, and therefore, a feasible option for bypassing the stall problem is to increase the flap deflection angle instead of the angle of attack for providing the required lift. Detailed analysis of the experimental results showed no relation between the flap angle and angle of attack.