Collaborative Airfoil Design for Dynamic Stall Performance

In this paper we present the results of a collaborative computational and experimental design process where airfoil sections that show improved stall performance are identified. The baseline design is the SC1094R8 airfoil section that in itself has superior stall performance than the SC1095 airfoil section. A formal design optimization study was carried out to identify candidate designs that could further delay the onset of stall on thin airfoils such as SC1094r8 airfoil section without substantially affecting other aerodynamic performance factors. Formal computational studies showed that simply adjusting the thickness of the SC1094R8 airfoil provided minimum benefit in improving stall performance. Therefore, the design study incorporated a broader design space that included modifying thickness, leading edge shape, suction side airfoil profile and droop as variables in facilitating shape change. A candidate design from the study was tested in a wind tunnel and found to show better performance (higher lift) and milder stall characteristics although the onset of stall was within the margins of experimental uncertainty. Subsequently, the design space was re-investigated and the airfoil section was modified to provide higher margins in delaying dynamic stall. This iterative process between simulations and experiments in deriving feasible designs is presented in the paper. Important conclusions that impact the design of airfoil sections such as the correlation of nose shape with type of stall, margins in the design process to accommodate experimental uncertainties are also discussed as part of a data mining exercise.