1. Title slide/end slide image dimensions: Title slide images must always fit this size: Height: 10.6 cm; Width: 25.4 cm Title slide images must always follow this position: Horizontal: 0 cm; Vertical: 0 cm To change title slide/end slide image: Contact Communication Support Tip: Vestas drawing guides will help you position and crop images and objects. Images and objects will snap to drawing guides when repositioned or cropped. To add drawing guides: Right-click on next to slide Select ‘Grid and Guides…’ Check ‘Display drawing guides on screen’ Press ‘OK’ Investigating wind quality for siting of wind turbines in complex terrain using an unsteady CFD method Vestas Technology R & D, Global Flow Solutions Cheng-Hu Hu 16th March 2011, EWEC 2011, Brussels, Belgium

2. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium2 Contents Introduction Methods Case studies Concluding remarks

3. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium3 Introduction More and more wind turbines have been sited at complex terrain. Challenges ￚ complex wind ￚ wind turbine performance Customers may ask ”The wind is there, why this wind turbine cannot perform as it is supposed to be?” Yes, we know complex wind can always have an effect on a wind turbine’s performance but we need to know more about it. Numerical simulation (CFD) is a tool we are using to study the local wind effects ￚ How turbulent is the wind? ￚ How does it look like if compared with the standard design code? ￚ Which part of wind turbine may suffer from the unfavourble flow behaviours?

4. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium4 Wind turbulence – fast change of flow behaviour Negative shear Positive shear Negative shear Positive shear Negative shear Positive shear

5. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium5 CFD – steady vs. unsteady methods Steady-state CFD simulation ￚ It is o.k. but it is not sufficient if we want to know how fast the wind can change from this second to next second ￚ Results are presented with mean values Unsteady CFD simulation ￚ Time series of wind velocity components can be produced ￚ More information about the wind turbulence ￚ Statistical analysis can be performed

6. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium6 Unsteady CFD – detached eddy simulation Free stream Detached eddies When eddy breaks, we say that the large eddies break into small eddies and the small eddies are “detached” from the mean flows

7. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium7 Methods - DES Detached eddy simulation (DES) ￚ RANS + LES ￚ SST k-ω model is used as the RANS model ￚ Focus is on the eddies ”detached” from the mean flows ￚ The ”detached eddies” usually can be found in complex terrain Ambient turbulence Detached eddies

8. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium8 Case study 1

9. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium9 Case 1 Streamwise velocity (-) Reverse flow (+)

10. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium10 Case 1 Very high wind shear and reverse flows have been observed

11. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium11 Case 1 Wind direction at rotor bottom is very irregular

12. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium12 Consequences of unfavourable wind

13. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium13 Case 2

14. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium14 Case 2 Rotor top Hub Rotor bottom Streamwise velocity (+)

15. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium15 Case 2 Large negative wind shear can occur

16. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium16 Case 2 Wind directions at rotor area is unsteady

17. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium17 Consequences of unfavourable wind

18. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium18 Wind shear and wind veer Tail outside IEC. High yaw Tail outside IEC. High tilt IEC 61400-1

19. Add presentation information via View/Header and Footer To add pre-formatted bullets please use the increase/decrease indent buttons found in the PowerPoint menu EWEC 2011 Brussels, Belgium19 Concluding remarks Unsteady CFD simulation can provide more information about flow properties For site development, with given wind conditions, we need to know ￚ Quantity of the wind (how much wind can be potentially converted to energy?) ￚ Quality of the wind (how good the wind turbine can perform?) QuantityQuality“Quantity” of the wind vs. “Quality” of the wind ￚ Global climate and mesoscale weather pattern determine the quantity of the wind ￚ Local terrain effects and micro climate determine the quality of the wind ￚ The quality of the wind has direct and immediate impact on wind turbine performance Better understanding of complex wind, better control of wind risk on wind turbines

20. Title slide/end slide image dimensions: Title slide images must always fit this size: Height: 10.6 cm; Width: 25.4 cm Title slide images must always follow this position: Horizontal: 0 cm; Vertical: 0 cm To change title slide/end slide image: Contact Communication Support Tip: Vestas drawing guides will help you position and crop images and objects. Images and objects will snap to drawing guides when repositioned or cropped. To add drawing guides: Right-click on next to slide Select ‘Grid and Guides…’ Check ‘Display drawing guides on screen’ Press ‘OK’ Copyright Notice The documents are created by Vestas Wind Systems A/S and contain copyrighted material, trademarks, and other proprietary information. All rights reserved. No part of the documents may be reproduced or copied in any form or by any means - such as graphic, electronic, or mechanical, including photocopying, taping, or information storage and retrieval systems without the prior written permission of Vestas Wind Systems A/S. The use of these documents by you, or anyone else authorized by you, is prohibited unless specifically permitted by Vestas Wind Systems A/S. You may not alter or remove any trademark, copyright or other notice from the documents. The documents are provided “as is” and Vestas Wind Systems A/S shall not have any responsibility or liability whatsoever for the results of use of the documents by you. Thank you for your attention