Tip-Vortex Investigation on a Rotating and Pitching Rotor Blade

The blade-tip vortex of a rotating and pitching DSA-9A blade was investigated numerically and experimentally. Numerical computations were performed using DLR, German Aerospace Center's finite volume solver TAU, and experimental data were gathered by using particle image velocimetry carried out in a stereoscopic setup at the rotor test facility in Göttingen. Algorithms deriving the vortex position, swirl velocity, circulation, and core radius were implemented. The agreement is better the lower the wake age is, with numerical dissipation enlarging the blade-tip vortex in an artificial manner with increasing wake age. Nevertheless, the numerical simulations are able to predict swirl velocity and circulation well and help understanding the growth and development of the blade-tip vortices. A comparison with a nonrotating version of this blade showed that the circulation of the nonrotating blade was in the same order