Effects of Camber on Dynamic Stall at Low Reynolds Numbers

The effects of camber on pitch-and-hold dynamic stall was investigated at a Reynolds number of 12,000 using high speed PIV. Three airfoil shapes (NACA 0012, Eppler 387, and SD 5060) and two dimensionless pitch rates (Ω* = 0.05 and 0.1) were studied undergoing pitching motions from 0 to 55 degrees angle of attack. Many previous observations, such as the effect of pitch rate on the formation location and formation angle of the Dynamic Stall Vortex (DSV), were also observed in this data set. Airfoil thickness was known to have an effect the formation of Shear Layer Vortices (SLVs). This work will demonstrate that SLV formation is instead determined by the amount of curvature on the upper surface as opposed to overall thickness. However, it remains true that the relative importance of the effects of airfoil shape compared to motion parameters is difficult to determine at these low pitch rates. This study will also show that the relationship between SLVs and Trailing Edge Vortices may be more important to the dynamic stall process than previous thought.