Experimental investigation of a helical vortex pair

Dominic Schröder (1) , Thomas Leweke (2) , Ralf Hörnschemeyer (1) , Eike Stumpf (1)

1 ILR - Institute of Aerospace Systems
2 IRPHE - Institut de Recherche sur les Phénomènes Hors Equilibre

We present the results from an experimental study of helical vortex pairs. A one-bladed rotor in the hover regime is investigated in a recirculating water channel by means of dye visualizations and stereoscopic particle image velocimetry. In order to generate a system consisting of two concentrated, closely spaced, helical vortices, the rotor blade is modified with a parametric fin placed near its tip. An exchangeable blade tip geometry allows a fast variation of the fin parameters, such as its spanwise position, height and angle of attack, which influence the characteristics of the tip vortex pair. Through this parameter variation it was possible to obtain a configuration in which the two vortices have almost the same circulation. They are found to rapidly merge into a single helical wake vortex. A comparison of the cases without and with fin concerning wake evolution and vortex parameters reveals that, after one blade rotation, the merged vortex resulting from the initial vortex pair has a significantly larger core radius than the single tip vortex without fin. This finding may have relevance in the context of Blade-Vortex Interactions, where noise generation and fatigue from fluid-structure interactions depend strongly on the vortex core size.

Mots clés: Rotor wake; Helical vortices; Merging; Dye visualization; Particle Image Velocimetry

Domaines: Mécanique des fluides [physics.class-ph]

Dominic Schröder, Thomas Leweke, Ralf Hörnschemeyer, Eike Stumpf. Experimental investigation of a helical vortex pair. Deutscher Luft- und Raumfahrtkongress 2020, Sep 2020, Aachen (online), Germany. ⟨hal-03053198⟩