Numerical and Experimental Investigations of Unsteady Flows under Deep Dynamic Stall Conditions

Abstract

With increasing advance ratios the retreating blades of modern helicopters encounter flow environments with severe separation and vortex shedding which are known as deep dynamic stall conditions. Recently considerable improvements have been achieved for both numerical methods and nonintrusive experimental flow diagnostic techniques to be applied to these complex highly unsteady flows. For the numerical treatment of the problem a time-accurate code based on the 2D-Navier-Stokes equations has been applied. The experimental investigation of the instantaneous flowfield was carried out by means of a Particle Image Velocimetry (PIV), in two different wind tunnel facilities: The low-speed wind tunnel of the German-French Institute, St. Louis (ISL) and the High Speed Wind tunnel (HKG) of the DLr in Goettingen. For each wind tunnel a test set-up for oscillating models exists and has been constructed and used throughout the measurements. Numerical and experimental data obtained under the same conditions will be presented and compared in the present paper.