Department of Aerospace Engineering and Center of Excellence in Computational Aerospace Engineering, Amirkabir University of Technology
Numerous experiments have been conducted on plunging Eppler 361 airfoil in a subsonic wind tunnel. The experimental tests involved measuring the surface pressure distribution over the airfoil at Re=1.5×105. The airfoil was equipped with Gurney flap(heights of 2.6, 3.3 and 5% chord) and plunged at 6cm amplitude. The unsteady aerodynamic loads were calculated from the surface pressure measurements, 51 ports, along with the chord on both upper and lower surfaces of the model. The Gurney flap effects over the loads hysteresis loops of the oscillating airfoil were particularly studied prior to stall, at the stall onset, in light stall, and deep stall conditions. The static results of the flapped and unflapped airfoil were also explored in order to make a reference of comparisonsto the dynamic loads.The results showed that, the addition of the Gurney flap provided no changes in the directions of the Cl, Cd and Cm hysteresis loops for the prior to stall flow conditions; while as a result of the positive camber effects, the lift hysteresis loops shifted upward and the pitching moment’s loops moved vertically downward. Additionally, adding the Gurney flap promoted dynamic stall phenomena.The deep dynamic stall of the flapped airfoil with the height of h/c=5% was seen at ads=13.1deg. This phenomenon was observed at ads=14.8deg for the flapped airfoils of h/c=2.6 and 3.3%.