Advertisement

Boundary-Layer Meteorology

, Volume 156, Issue 3, pp 395–413 | Cite as

A Wind-Tunnel Simulation of the Wake of a Large Wind Turbine in a Weakly Unstable Boundary Layer

  • P. E. Hancock
  • S. Zhang
Article

Abstract

Measurements have been made in the wake of a model wind turbine in both a weakly unstable and a baseline neutral atmospheric boundary layer, in the EnFlo stratified-flow wind tunnel, between 0.5 and 10 rotor diameters from the turbine, as part of an investigation of wakes in offshore winds. In the unstable case the velocity deficit decreases more rapidly than in the neutral case, largely because the boundary-layer turbulence levels are higher with consequent increased mixing. The height and width increase more rapidly in the unstable case, though still in a linear manner. The vertical heat flux decreases rapidly through the turbine, recovering to the undisturbed level first in the lower part of the wake, and later in the upper part, through the growth of an internal layer. At 10 rotor diameters from the turbine, the wake has strong features associated with the surrounding atmospheric boundary layer. A distinction is drawn between direct effects of stratification, as necessarily arising from buoyant production, and indirect effects, which arise only because the mean shear and turbulence levels are altered. Some aspects of the wake follow a similarity-like behaviour. Sufficiently far downstream, the decay of the velocity deficit follows a power law in the unstable case as well as the neutral case, but does so after a shorter distance from the turbine. Tentatively, this distance is also shorter for a higher loading on the turbine, while the power law itself is unaffected by turbine loading.

Keywords

Atmospheric boundary layer Unstable boundary layer  Wind-tunnel experiment Wind-turbine wakes 

Notes

Acknowledgments

The work reported here was done under the SUPERGEN programme of the Engineering and Physical Sciences Research Council, SUPERGEN-Wind Phase 2, reference EP/H018662/1. Further details can be found from http://www.supergenwind.org.uk. The authors are particularly grateful to Dr. P. Hayden, for assistance in setting up the experiments, and to Prof. A. G. Robins, for useful discussions and comment during the programme of research. The EnFlo wind tunnel is a NERC/NCAS national facility, and the authors are also grateful to NCAS for the support provided.

References

  1. Abkar M, Porté-Agel F (2014) The effect of atmospheric stability on wind-turbine wakes: a large-eddy simulation study. The Science of Making Torque from Wind 2014. J Phys 524, 012138, 9 ppGoogle Scholar
  2. Argyle P, Watson S (2012) A study of the surface layer atmospheric stability at two UK offshore sites. In: European wind energy association conference, 16–19 Apr 2012, Copenhagen, DenmarkGoogle Scholar
  3. Baker RW, Walker SN (1984) Wake measurements behind a large horizontal axis wind turbine generator. Sol Energy 33:5–12CrossRefGoogle Scholar
  4. Barthelmie RJ, Pryor SC, Frandsen ST, Hansen KS, Schepers JG, Rados K, Schelz W, Neubert A, Jensen LE, Neckelmann S (2010) Quantifying the impact of wind turbine wakes on power output at offshore wind farms. J Atmos Ocean Technol 27:1302–1317CrossRefGoogle Scholar
  5. Barthelmie RJ, Frandsen ST, Rathmann O, Hansen K, Politis ES, Prospathopoulos J, Schepers JG, Rados K, Cabezón D, Schlez W, Neubert A, Heath M (2011) Flow and wakes in large wind farms: final report for UpWind WP8. Risø report Risø-R-1765(EN)Google Scholar
  6. Bastankhan M, Porté-Agel F (2014) A new analytical model for wind turbines. Renew Energy 70:116–123CrossRefGoogle Scholar
  7. Chamorro LP, Porté-Agel F (2010) Effects of thermal stability and incoming boundary-layer flow characteristics on wind turbine wakes: a wind tunnel study. Boundary-Layer Meteorol 136:515–533CrossRefGoogle Scholar
  8. ESDU (2001) Characteristics of atmospheric turbulence near the ground. Part II: Single point data for strong winds (neutral atmosphere). ESDU 85020. Engineering Sciences Data Unit, London, 42 ppGoogle Scholar
  9. ESDU (2002) Strong winds in the atmospheric boundary layer. Part 1: Hourly-mean wind speeds. ESDU 85026. Engineering Sciences Data Unit, London, 61 ppGoogle Scholar
  10. Hancock PE, Zhang S, Pascheke F, Hayden P (2012) Wind tunnel simulation of wind turbine wakes in stable and unstable wind flow. In: Science of making torque from wind conference, 9–11 Oct, OldenburgGoogle Scholar
  11. Hancock PE (2013) Wind turbines in series: a parametric analysis. J Wind Eng 37:37–58CrossRefGoogle Scholar
  12. Hancock PE, Pascheke F, Zhang S (2014) Wind tunnel simulation of wind turbine wakes in neutral, stable and unstable offshore atmospheric boundary layers. In: Conference on wind energy—impact of turbulence. Research Topics in Wind Energy, vol 2. Springer, New YorkGoogle Scholar
  13. Hancock PE, Farr TD (2014) Wind-tunnel simulations of wind-turbine arrays in neutral and non-neutral winds. The Science of Making Torque from Wind 2014. J Phys 524, 012166, 12 ppGoogle Scholar
  14. Hancock PE, Pascheke F (2014a) Wind tunnel simulation of the wake flow of a large wind turbine in a stable boundary layer. Part 1: The boundary layer simulation. Boundary-Layer Meteorol 151:3–21CrossRefGoogle Scholar
  15. Hancock PE, Pascheke F (2014b) Wind tunnel simulation of the wake flow of a large wind turbine in a stable boundary layer. Part 2: The wake flow. Boundary-Layer Meteorol 151:23–37CrossRefGoogle Scholar
  16. Hancock PE, Zhang S, Hayden P (2013) A wind-tunnel artificially-thickened weakly-unstable atmospheric boundary layer. Boundary-Layer Meteorol 149:355–380CrossRefGoogle Scholar
  17. Hansen KS, Barthelmie RJ, Jensen LE, Sommer A (2012) The impact of turbulence intensity and atmospheric stability in power deficits due to wind turbine wakes at Horns Rev wind farm. Wind Energy 15:183–196CrossRefGoogle Scholar
  18. Hansen KS, Larsen GC, Ott S (2014) Dependence of offshore wind turbine fatigue loads on atmospheric stratification. The Science of Making Torque from Wind 2014. J Phys 524, 012165, 13 ppGoogle Scholar
  19. Hassan U (1993) Wind tunnel investigation of the wake structure within small wind farms. Energy Technology Support Unit, UK, report ETSU WN 5113, 2004 ppGoogle Scholar
  20. Heist DK, Castro IP (1998) Combined laser-Doppler and cold-wire anemometry for turbulent heat flux measurement. Exp Fluids 24:45–76CrossRefGoogle Scholar
  21. Högström U, Asimakopoulos DN, Kambezidis H, Helmis CG, Smedman A (1988) A field study of the wake behind a 2MW wind turbine. Atmos Environ 22:803–820CrossRefGoogle Scholar
  22. Irwin HPAH (1981) The design of spires for wind stimulation. J Wind Eng Ind Aerodyn 7:361–366CrossRefGoogle Scholar
  23. Iungo GV, Porté-Agel F (2014) Volumatric LiDAR scanning of wind turbine wakes under convective and neutral atmospheric stability regimes. J Atmos Ocean Technol 31:2035–2048CrossRefGoogle Scholar
  24. Magnusson M, Smedman A-S (1994) Influence of atmospheric stability on wind turbine wakes. J Wind Eng 18:139–153Google Scholar
  25. Magnusson M, Smedman A-S (1996) A practical method to estimate the wind turbine wake characteristics from turbine data and routine wind measurements. J Wind Eng 20:73–92Google Scholar
  26. Magnusson M, Smedman A-S (1999) Air flow behind wind turbines. J Wind Eng Ind Aerodyn 80:169–189CrossRefGoogle Scholar
  27. Motta M, Barthelmie RJ (2005) The influence of non-logarithmic wind speed profiles on potential power output of Danish offshore sites. Wind Energy 8:219–236CrossRefGoogle Scholar
  28. Ohya Y, Uchida T (2004) Laboratory and numerical studies of the convective boundary layer capped by a strong inversion. Boundary-Layer Meteorol 112:223–240CrossRefGoogle Scholar
  29. Peña A, Réthoré P-E, Rathman O (2014) Modelling large offshore wind farms under different atmospheric regimes with the Park wake model. Renew Energy 70:164–171CrossRefGoogle Scholar
  30. Sanderse B, van der Pijl SP, Koren B (2011) Review of computational fluid dynamics for wind turbine wake aerodynamics. Wind Energy 14:799–819CrossRefGoogle Scholar
  31. Sathe A, Bierbooms A (2007) Influence od different wind profiles due to varying atmospheric stability on the fatigue life of wind turbines. Science of Making Torque from Wind, 2007. J Phys 75, 012056, 7 ppGoogle Scholar
  32. Stull RB (1988) An introduction to boundary layer meteorology. Kluwer Academic Publishers, Dordrecht, 666 ppGoogle Scholar
  33. Townsend AA (1976) The structure of turbulent shear flow. Cambridge University Press, Cambridge, 450 ppGoogle Scholar
  34. Trujillo J-J, Bingol F, Larsen GC, Mann J, Kühn M (2011) Ligt detection and ranging measurements of wake dynamics. Part II: Two-dimensional scanning. Wind Energy 14:61–75CrossRefGoogle Scholar
  35. van den Berg GP (2008) Wind turbine power and sound in relation to atmospheric stability. Wind Energy 11:151–169CrossRefGoogle Scholar
  36. Wagner R, Antoniou I, Pedersen AM, Courtney MS, Jørgensoen HE (2009) The influence of wind speed profile on wind turbine performance measurements. Wind Energy 12:348–362CrossRefGoogle Scholar
  37. Wharton S, Lundquist JK (2010) Atmospheric stability impacts in power curves of tall wind turbines—an analysis of a west coast North American wind farm. Report Lawrence Livermore National Laboratory LLNL-TR-424425, 73 ppGoogle Scholar
  38. Zhang W, Markfort CD, Porté-Agel F (2013) Wind-turbine wakes in a convective boundary layer: a wind tunnel study. Boundary-Layer Meteorol 136:515–533Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  1. 1.EnFlo Laboratory, Faculty of Engineering and Physical SciencesUniversity of SurreyGuildfordUK
  2. 2.School of Mechanical, Aerospace and Civil EngineeringUniversity of ManchesterManchesterUK

Personalised recommendations