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Research articles 09 May 2018

Research articles | 09 May 2018

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This discussion paper is a preprint. A revision of the manuscript is under review for the journal Wind Energy Science (WES).

Numerical Analyses and Optimizations on the Flow in the Nacelle Region of a Wind Turbine

Pascal Weihing1, Tim Wegmann1, Thorsten Lutz1, Ewald Krämer1, Timo Kühn2, and Andree Altmikus2 Pascal Weihing et al.
  • 1Institute of Aerodynamics and Gas Dynamics, University of Stuttgart, Pfaffenwaldring 21, 70563 Stuttgart, Germany
  • 2Wobben Research & Development GmbH, Bosridgstraße 26, 26607 Aurich, Germany

Abstract. The present study investigates the flow dynamics in the hub region of a wind turbine focusing on the influence of the nacelle geometry on the root aerodynamics by means of Reynolds averaged Navier-Stokes simulations with the code FLOWer. The turbine considered is a generic version of the Enercon E44 converter incorporating blades with flatback-profiled root sections. First, a comparison is drawn between an isolated rotor assumption and a setup including the baseline geometry, in order to elaborate the basic flow features of the blade root. It was found that the nacelle reduces the trailed circulation of the root vortices and improves aerodynamic efficiency for the inner portion of the rotor, but on the other hand induces a complex vortex system in the junction of the blade and the nacelle that causes flow separation. The origin of these effects is analyzed in detail. In a second step, effects of basic geometric nacelle properties have been analyzed with the purpose to increase the aerodynamic efficiency in the root region. Therefore, three modification categories have been addressed, where the first alters the nacelle diameter, the second varies the blade position relative to the nacelle and the third comprises modifications in the vicinity of the blade-nacelle junction. The impact of the geometrical modifications on the local flow physics are discussed and assessed with respect to aerodynamic performance in the blade root region. It was found that increasing the nacelle diameter deteriorates the root aerodynamics, since the flow separation gets more pronounced. Possible solutions identified to reduce the flow separation are a shift of the blade in direction of the rotation or the installation of a fairing fillet in the junction between the blade and the nacelle.

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Pascal Weihing et al.
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Pascal Weihing et al.
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Latest update: 17 Jul 2018
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Short summary
This research poses the question, whether rotor performance can be increased by an optimized design of the nacelle. For this purpose, the main geometrical parameters of the nacelle, as the diameter, the relative position of the blade or the detailed shape in the junction of the blade are investigated by means of Computational Fluid Dynamics. By implementing a fairing type shape in the junction, the detrimental flow separation in the inner part of the rotor could be eliminated.
This research poses the question, whether rotor performance can be increased by an optimized...