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https://doi.org/10.5194/wes-2018-3
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Research articles 18 Jan 2018

Research articles | 18 Jan 2018

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

Dynamic inflow effects in measurements and high fidelity computations

Georg R. Pirrung and Helge Aa. Madsen Georg R. Pirrung and Helge Aa. Madsen
  • Wind Energy Department, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde, Denmark

Abstract. A wind turbine experiences an overshoot in loading after for example a collective step change in pitch angle. This overshoot occurs because the wind turbine wake does not immediately reach its new equilibrium, an effect usually referred to as dynamic inflow. Analycal vortex models and actuator disc simulations predict that the time constants of this dynamic inflow effect should decrease significantly towards the blade tip. As part of the NASA Ames Phase VI experiment pitch steps have been performed on a turbine in controlled conditions in the wind tunnel. The measured aerodynamic forces from these experiments seemed to show much less radial dependency of the dynamic inflow time constants than expected when pitching towards low loading. Moreover the dynamic inflow effect seemed fundamentally different when pitching from low to high loading, and the reason for this behavior remained unclear in previous analyses of the experiment. High fidelity computational fluid dynamics and free wake vortex code computations yielded the same behavior as the experiments. In the present work these observations from the experiments and high fidelity computations are explained based on a simple vortex cylinder wake model.

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Georg R. Pirrung and Helge Aa. Madsen
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Georg R. Pirrung and Helge Aa. Madsen
Georg R. Pirrung and Helge Aa. Madsen
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Short summary
A wind turbine sees an overshoot in loading after a step change in pitch angle because the wake takes some time to reach a new equilibrium. The time constants of this dynamic inflow effect are expected to decrease significantly towards the blade tip. This radial dependency has not been found to the expected extent in previous analyses of force measurements from the NASA Ames Phase VI experiment. In the present article the findings from the experiment are explained based on a simple vortex model.
A wind turbine sees an overshoot in loading after a step change in pitch angle because the wake...
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