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

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 turbine was positioned in the free stream, near the entrance of the 6 m×2.7 m cross section of the University of New Hampshire (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 hot-wire anemometry with a multiwire sensor were used to obtain velocity field measurements in the wake of the model turbine up to 20 diameters downstream. The results of an equilibrium similarity 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.

[1]  Neil Kelley,et al.  Comparing Pulsed Doppler LIDAR with SODAR and Direct Measurements for Wind Assessment , 2007 .

[2]  Peter B. V. Johansson,et al.  The Axisymmetric Turbulent Wake , 2002 .

[3]  Barbara T. Fichman.  Annual Energy Review 2011 , 2012 .

[4]  Leo E. Jensen,et al.  Quantifying the Impact of Wind Turbine Wakes on Power Output at Offshore Wind Farms , 2010 .

[5]  Jonathan W. Naughton,et al.  An Experimental Study of the Far-Field of an Incompressible Swirling Jet , 2005 .

[6]  B. Lange,et al.  Comparison of Wake Model Simulations with Offshore Wind Turbine Wake Profiles Measured by Sodar , 2006 .

[7]  J. Sørensen,et al.  Wind turbine wake aerodynamics , 2003 .

[8]  Robert D. Moser,et al.  Self-similarity of time-evolving plane wakes , 1998, Journal of Fluid Mechanics.

[9]  Michael J. Gourlay,et al.  Equilibrium similarity, effects of initial conditions and local Reynolds number on the axisymmetric wake , 2003 .

[10]  S. Butterfield,et al.  Improving Wind Turbine Gearbox Reliability , 2007 .

[11]  J. Lundquist,et al.  The modification of wind turbine performance by statistically distinct atmospheric regimes , 2012 .

[12]  James F. Manwell,et al.  Optimizing the layout of offshore wind energy systems , 2008 .

[13]  Jonathan W. Naughton,et al.  Experimental Study of the Far Field of Incompressible Swirling Jets , 2008 .

[14]  G. Larsen,et al.  Light detection and ranging measurements of wake dynamics part I: one‐dimensional scanning , 2010 .

[15]  C. Meneveau,et al.  Experimental study of the horizontally averaged flow structure in a model wind-turbine array boundary layer , 2009 .

[16]  Shuangwen Sheng,et al.  Wind Turbine Micropitting Workshop: A Recap , 2010 .