Boundary-Layer Meteorology

, 141:245 | Cite as

The Bolund Experiment, Part II: Blind Comparison of Microscale Flow Models

  • A. Bechmann
  • N. N. Sørensen
  • J. Berg
  • J. Mann
  • P.-E. Réthoré
Open Access


Bolund measurements were used for a blind comparison of microscale flow models. Fifty-seven models ranging from numerical to physical were used, including large-eddy simulation (LES) models, Reynolds-averaged Navier–Stokes (RANS) models, and linearized models, in addition to wind-tunnel and water-channel experiments. Many assumptions of linearized models were violated when simulating the flow around Bolund. As expected, these models showed large errors. Expectations were higher for LES models. However, of the submitted LES results, all had difficulties in applying the specified boundary conditions and all had large speed-up errors. In contrast, the physical models both managed to apply undisturbed ‘free wind’ boundary conditions and achieve good speed-up results. The most successful models were RANS with two-equation closures. These models gave the lowest errors with respect to speed-up and turbulent kinetic energy (TKE) prediction.


Bolund Blind comparison Complex terrain Computational fluid dynamics Microscale Validation 



We would like to thank the Danish Energy Agency (EFP07—Metoder til kortlægning af vindforhold i komplekst terræn (ENS-33033-0062), the Center for Computational Wind Turbine Aerodynamics and Atmospheric Turbulence (under the Danish Council for Strategic Research, Grant No. 09-067216) and Vestas Technology R&D for financial support. We would also like to thank former Risø DTU employee Jeppe Johansen, who envisioned the concept of a field campaign at Bolund and initiated the project together with Hans E. Jørgensen. Without the aid of the technicians in the Test and Measurement section in the wind energy division at Risø DTU, as well as all those Risø DTU employees who helped carrying masts and instruments, this project would not have been possible. Computations were made possible by the use of the Thyra PC-cluster at Risø DTU and DCSC, PC-cluster Yggdrasil. Finally, a special thanks goes to all anonymous contributors who made the blind comparison possible.

Open Access

This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.


  1. Andren A, Brown A, Graf J, Moeng C, Mason P, Nieuwstadt F, Schumann U (1994) Large-eddy simulation of a neutrally stratified boundary layer: a comparison of four computer codes. Q J Roy Meteorol Soc 120: 1457–1484CrossRefGoogle Scholar
  2. Apsley D, Castro I (1997) A limited-length-scale k-\({\varepsilon}\) model for the neutral and stably-stratified atmospheric boundary layer. Boundary-Layer Meteorol 83: 75–98CrossRefGoogle Scholar
  3. Athanassiadou M, Castro I (2001) Neutral flow over a series of rough hills: a laboratory experiment. Boundary-Layer Meteorol 101: 1–30CrossRefGoogle Scholar
  4. Bechmann A, Sørensen N (2010a) Hybrid RANS/LES applied to complex terrain. Wind Energy. doi: 10.1002/we.414
  5. Bechmann A, Sørensen N (2010b) Hybrid RANS/LES method for wind flow over complex terrain. Wind Energy 13: 36–50. doi: 10.1002/we.246 CrossRefGoogle Scholar
  6. Bechmann A, Berg J, Courtney M, Jørgensen H, Mann J, Sørensen N (2009) The Bolund experiment: overview and background. Risø DTU report Risø-R1658(EN), 50 ppGoogle Scholar
  7. Beljaars A, Walmsley J, Taylor P (1987) A mixed spectral finite difference model for neutrally stratified boundary layer flow over roughness changes and topography. Boundary-Layer Meteorol 38: 273–303CrossRefGoogle Scholar
  8. Berg J, Mann J, Bechmann A, Courtney M, Jørgensen H (2011) The Bolund experiment, part I: flow over a steep, three-dimensional hill. Boundary-Layer Meteorol (this issue)Google Scholar
  9. Bradley E (1980) An experimental study of the profiles of wind speed, shearing stress and turbulence at the crest of a large hill. Q J Roy Meteorol Soc 106: 101–123CrossRefGoogle Scholar
  10. Brown A, Hobson J, Wood N (2001) Large-eddy simulation of neutral turbulent flow over rough sinusoidal ridges. Boundary-Layer Meteorol 98: 411–441CrossRefGoogle Scholar
  11. Castro F, Snyder W (1982) A wind tunnel study of the dispersion from sources downwind of three-dimensional hills. Atmos Environ 16(8): 1869–1887CrossRefGoogle Scholar
  12. Castro F, Palma J, Silva Lopes A (2003) Simulation of the Askervein flow. part 1: Reynolds averaged Navier-Stokes equations (k-\({\varepsilon}\) turbulence model). Boundary-Layer Meteorol 107: 501–530CrossRefGoogle Scholar
  13. Chow F, Street R (2009) Evaluation of turbulence closure models for large-eddy simulation over complex terrain: flow over Askervein Hill. J Appl Meteorol 48(5): 1050–1065. doi: 10.1175/2008JAMC1862.1 CrossRefGoogle Scholar
  14. Chow F, Weigel A, Street R, Rotach M, Xue M (2006) High-resolution large-eddy simulations of flow in a steep alpine valley. Part I: methodology, verification, and sensitivity experiments. J Appl Meteorol 45(1): 63–86CrossRefGoogle Scholar
  15. Detering E, Etling E (1985) Application of the e-\({\varepsilon}\) turbulence model to the atmospheric boundary layer. Boundary-Layer Meteorol 33: 113–133CrossRefGoogle Scholar
  16. Duynkerke P (1987) Application of the e-\({\epsilon}\) turbulence closure model to the neutral and stable atmospheric boundary layer. J Atmos Sci 45: 865–880CrossRefGoogle Scholar
  17. Eidsvik K (2005) AA system for wind power estimation in mountainous terrain. Prediction of Askervein Hill data. Wind Energy 8: 237–249CrossRefGoogle Scholar
  18. Emeis S, Højstrup M, Jensen N (1993) Hjardemål experiment data report. Risø DTU report Risø-M-2289(EN), 126 ppGoogle Scholar
  19. Hunt J, Snyder W (1980) Experiments on stable and neutrally stratified flow over a model three-dimensional hill. J Fluid Mech 96(4): 671–704CrossRefGoogle Scholar
  20. Jackson P, Hunt J (1975) Turbulent wind flow over a low hill. Q J Roy Meteorol Soc 101: 929–955CrossRefGoogle Scholar
  21. Jenkins G, Mason P, Moores W, Stykes R (1981) Measurements of the flow structure around Ailsa Craig, a steep, three-dimensional, isolated hill. Q J Roy Meteorol Soc 107: 833–851CrossRefGoogle Scholar
  22. Jensen N, Petersen E, Troen I (1984) Extrapolation of mean wind statistics with special regard to wind energy applications. World Meteorological Organization WCP-86, pp 1–85Google Scholar
  23. Kim H, Patel V (2000) Test of turbulence models for wind flow over terrain with separation and recirculation. Boundary-Layer Meteorol 94: 5–21CrossRefGoogle Scholar
  24. Launder B, Spalding D (1974) The numerical computation of turbulent flows. Comput Mech Appl Mech Eng 3: 269–289CrossRefGoogle Scholar
  25. Mason P, King J (1985) Measurements and predictions of flow and turbulence over an isolated hill of moderate slope. Q J Roy Meteorol Soc 111: 617–640CrossRefGoogle Scholar
  26. Mason P, Stykes R (1979) Flow over an isolated hill of moderate slope. Q J Roy Meteorol Soc 105: 383–395CrossRefGoogle Scholar
  27. Mason P, Thomson D (1992) Stochastic backscatter in large-eddy simulations of boundary layer. J Fluid Mech 24: 51–78CrossRefGoogle Scholar
  28. Panofsky H, Dutton J (1984) Atmospheric turbulence models and methods for engineering applications. John Wiley and Sons, New York, 397 ppGoogle Scholar
  29. Porté-Agel F, Meneveau C, Parlange M (2000) A scale-dependent dynamic model for large-eddy simulation: application to a neutral atmospheric boundary layer. J Fluid Mech 415: 261–284CrossRefGoogle Scholar
  30. Raithby G, Stubley G, Taylor P (1987) The Askervein Hill project: a finite control volume prediction of three-dimensional flows over the hill. Boundary-Layer Meteorol 39: 247–267CrossRefGoogle Scholar
  31. Røkenes K, Krogstad PÅ (2009) Wind tunnel simulation of terrain effects on wind farm siting. Wind Energy 12: 391–410CrossRefGoogle Scholar
  32. Salmon R, Teunissen H, Mickle R, Taylor P (1988) The kettles hill project: field observations, wind-tunnel simulations and numerical model predictions for flow over a low hill. Boundary-Layer Meteorol 43: 309–342CrossRefGoogle Scholar
  33. Silva Lopes A, Palma J, Castro F (2007) Simulation of the Askervein flow. Part 2: large-eddy simulations. Boundary-Layer Meteorol 125: 85–108CrossRefGoogle Scholar
  34. Simms D, Schreck S, Hand M, Fingersh L (2001) NREL unsteady aerodynamics experiment in the Nasa-Ames wind tunnel: a comparison of predictions to measurements. National Renewable Energy Laboratory NREL/TP-500-29494, 51 ppGoogle Scholar
  35. Sullivan P, McWilliams J, Moeng CH (1994) A subgrid-scale model for large-eddy simulation of planetary boundary layer. Boundary-Layer Meteorol 71: 247–276CrossRefGoogle Scholar
  36. Taylor PA (1977) Some numerical studies of surface boundary-layer flow above gentle topography. Boundary-Layer Meteorol 11: 439–465CrossRefGoogle Scholar
  37. Taylor PA, Teunissen H (1987) The Askervein Hill project: overview and background data. Boundary-Layer Meteorol 39: 15–39CrossRefGoogle Scholar
  38. Taylor PA, Walmsley J, Salmon J (1983) A simple model of neutrally stratified boundary-layer flow over real terrain incorporating wavenumber-dependent scaling. Boundary-Layer Meteorol 26: 169–189CrossRefGoogle Scholar
  39. Troen I, Petersen E (1989) European wind atlas. Risø National Laboratory, Roskilde ISBN: 87-550-1482-8, 656 ppGoogle Scholar
  40. Undheim O, Andersson H, Berge E (2006) Non-linear, microscale modelling of the flow over Askervein Hill. Boundary-Layer Meteorol 120: 477–495CrossRefGoogle Scholar
  41. Walmsley J, Taylor P (1996) Boundary-layer flow over topography: impacts of the Askervein study. Boundary-Layer Meteorol 78: 291–320CrossRefGoogle Scholar
  42. Walmsley J, Taylor P, Keith T (1986) A simple model of neutrally stratified boundary-layer flow over complex terrain with surface roughness modulations (ms3djh/3r). Boundary-Layer Meteorol 36: 157–186CrossRefGoogle Scholar
  43. Walmsley J, Troen I, Lalas D, Mason P (1990) Surface-layer flow in complex terrain: comparison of models and full-scale observations. Boundary-Layer Meteorol 52: 259–281CrossRefGoogle Scholar
  44. Wan F, Porte-Agel F, Stoll R (2007) Evaluation of dynamic subgrid-scale models in large-eddy simulations of neutral turbulent flow over a two-dimensional sinusoidal hill. Atmos Environ 41(13): 2719–2728CrossRefGoogle Scholar
  45. Weigel A, Chow F, Rotach M, Street R, Xue M (2006) High-resolution large-eddy simulations of flow in a steep alpine valley. Part II: flow structure and heat budgets. J Appl Meteorol 45(1): 87–107CrossRefGoogle Scholar
  46. Wood N (1995) The onset of separation in neutral, turbulent flow over hills. Boundary-Layer Meteorol 76: 137–164CrossRefGoogle Scholar
  47. Xu D, Taylor P (1997) An e-\({\epsilon}\) -l turbulence closure scheme for planetary boundary-layer models: the neutrally stratified case. Boundary-Layer Meteorol 84: 247–266CrossRefGoogle Scholar
  48. Zeman O, Jensen N (1987) Modification of turbulence characteristics in flow over hills. Q J Roy Meteorol Soc 113: 55–80CrossRefGoogle Scholar

Copyright information

© The Author(s) 2011

Authors and Affiliations

  • A. Bechmann
    • 1
  • N. N. Sørensen
    • 1
  • J. Berg
    • 1
  • J. Mann
    • 1
  • P.-E. Réthoré
    • 1
  1. 1.The Wind Energy DepartmentRisø National Laboratory for Sustainable Energy/Technical University of DenmarkRoskildeDenmark

Personalised recommendations