Analysis of Configurational Parameters on the Vortex System of a Rotor

Abstract

The wake of a rotor is a complex three-dimensional flow, which is dominated by unsteady aerodynamic effects. In general, the wake is characterized by the helix-shaped trailing blade tip vortices, the blade shear layers, the rotorinduced downwash velocity field and the external flow conditions. The interaction of these mechanisms results in the breakdown of the vortex system with its downward propagation. The blade tip vortices, which are initially well defined, begin to decompose with increasing wake age. Due to its complexity, the numerical simulation of this breakdown is still challenging and therefore part of current research activities. The vortex interaction and decomposition are highly relevant to the efficiency and noise development of rotors, especially for hover flight cases. Accordingly, these effects need to be investigated in detail. In recent publications additional s-shaped vortex worms, in between the blade tip vortices, were observed. A so formed vortex system is sketched in Fig. 1a. This presentation will also focus on their contribution to vortex breakdown.