An experimental study on aerodynamics of NACA2415 aerofoil at low Re numbers

► A detailed experimental study on aerodynamics of NACA2415 aerofoil at low Re numbers. ► As angle of attack and Re number increase, bubble and transition point move towards leading edge. ► Bubble size increases and stall angle decreases with decreasing Re number. ► As Re number decreases, stall abruptness increases. ► At lower Re numbers short bubble bursts at higher incidences and long bubble occurs. This study is a detailed experimental investigation on aerodynamics of a NACA2415 aerofoil by varying angle of attack from −12° to 20° at low Reynolds number flight regimes (0.5×105 to 3×105). For this investigation, pressure distributions over the aerofoil were measured using a system including a pitot-static tube, a scanivalve unit and a pressure transducer. Moreover, time-dependant lift and drag forces and pitch moment of the aerofoil were obtained by using an external three-component load-cell system. Velocity measurements at different points over the aerofoil were carried out by using a hot-wire anemometer, and oil flow visualization method was used to photograph the surface flow patterns. The experimental results showed that as the angle of attack increased, the separation and the transition points moved towards the leading edge at all Reynolds numbers. Furthermore as the Reynolds number increased, stall characteristic changed and the mild stall occurred at higher Reynolds numbers whereas the abrupt stall occurred at lower Reynolds numbers. The stall angle varied with Re number due to the viscous effects and decreased with decreasing Re number. By the decreasing of the Re number, short bubble burst at higher angles of attack, which caused long bubble to occur.