Measurement of Dynamic Stall on the DU Wind Turbine Airfoil Series

Pitch-oscillating wind-turbine airfoils have been studied using unsteady surface pressure measurements as well as phase-locked flow-field measurements. From a number of blade geometry and oscillation conditions studied, four characteristic types of stall have been identified: (i) trailing edge stall, (ii) trailing edge stall with a secondary vortex, (iii) trailing edge stall with a separation vortex replacement, and (iv) trailing edge stall followed by a leading edge stall. Each of these types of stall has been identified by examining the unsteady pressure distribution and flow-field structure associated with particular case. The data from this study should prove useful to modelers trying to capture the complex physics associated with these flows.