Joukowski’s wake model for tip-splitting rotors
Orateur : Andrés Castillo
Abstract : The interaction between a tip vortex and a solid surface is responsible for premature structural component fatigue in wind turbines and undesirable noise in helicopter rotors during low speed and descending flight. One noise reduction strategy uses a modified airfoil to split and spread the vorticity in two tip vortices. The present paper aims to provide the wake structure produced by such a rotor for wind turbine and helicopter regimes. We use a filamentary approach, such that vortices are assumed to roll-up quickly to form thin vortex filaments of finite but small size and compute the induced velocity using a cut-off method. We study the stability to long-wave displacements by means of a linear impulse response analysis. To do so, we characterize the near- and far-fields separately. The resulting wake has a dual nature and is well-described by a twisted vortex pair locally aligned along with a larger helical structure. The wake is linearly unstable and subject to two kinds of pairing modes : between successive turns of the large helical structure and the successive turns of the vortex pair.
Date et lieu : le vendredi 12 mars à 11h00 / IRPHE
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