Velocity Deficit and Swirl in the Turbulent Wake of a Wind Turbine

Authors: N. Dufresne and M. Wosnik

This article, published in the Marine Technology Society Journal, describes a theoretical and experimental investigation into the wake of an axial-flow turbine in a wind tunnel.

Abstract

Energy production data from several of the existing large offshore wind farms indicate that turbine arrays can suffer from a significant overall energy production shortfall, due to wakes generated by turbines upstream interacting with turbines downstream. An experimental investigation of the axial and azimuthal (swirl) velocity field in the wake of a single three-bladed wind turbine with rotor diameter of 0.91 m was conducted. The turbinewas positioned in the free stream, near the entrance of the 6 m × 2.7 m cross section of the UNH Flow Physics Facility, a 72-m-long boundary layer wind tunnel. The turbine model was tested at various rotor loading conditions with blade tip-speed ratios up to 2.8. A Pitot-static tube and constant temperature hotwire anemometry with a multiwire sensor were used to obtain velocity field measurements in the wake of themodel turbine up to 20 diameters downstream. The results of an equilibriumsimilarity theory for the axisymmetric wake with rotation are presented. The measurements obtained were used to examine the validity of the derived scaling functions for streamwise and azimuthal velocity, wake growth, and turbulence.

Citation

@ARTICLE{
  author = {Nathaniel P. Dufresne and Martin Wosnik},
  title = {Velocity Deficit and Swirl in the Turbulent Wake of a Wind Turbine},
  journal = {Marine Technology Society Journal},
  year = {2013},
  volume = {47},
  pages = {193-205}
}

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