Unsteady Airfoil Design Optimization with Application to Dynamic Stall

Dynamic stall in rotorcraft blades still remains a challenging problem for the US Army since it limits the operability, maneuverability and flight speed of the rotorcraft. There are numerous documented instances of large impulsive blade pitching moments and loss of lift resulting from dynamic stall events.In this proposal our primary goal is experimental testing and verification of the performance of optimized airfoil sections that delay the onset of stall.The experiments are critical since the margins for design improvement are small but the overall payoff in alleviating dynamic stall remains very significant for the reliable operation of the current fleet of rotorcraft.A comprehensive analysis of the modified rotor blade with the optimized airfoil sections will be carried out to ensure suppression of dynamic stall events.Furthermore, the transient aerodynamic loads and detailed PIV visualization obtained from dynamic testing can be used to improve turbulence modeling procedures and better understand the transient events that initiate the processes that ultimately lead to the formation of the large-scale dynamic stall vortex and result in full blown dynamic stall.Lastly, the CFD-code used in dynamic stall design with its upgraded turbulence models will be integrated into the Helios Framework.