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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Karim Fahssis MeteoPole Zephy-Science, France
Co-authors:
Karim Fahssis (1) F Ming Peng (2)
(1) MeteoPole Zephy-Science, Marseille, France (2) Guangdong Province Wind Power Generation Co.,Ltd, Guangzhou, China

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Karim Fahssis is a well-known wind energy expert with a deep knowledge and hands-on experience of all the stages of a wind power project : from site selection to power performance optimization through bankable assessments and micrositing. Karim Fahssis was recently awarded by the MIT Technology Review as the "Innovator of the year 2014" for introducing path breaking software technologies to the wind industry.

Karim holds a double master’s degree in mechanical engineering and fluid dynamics from Centrale Nantes engineering school (France) and energy management from the Xi’an Jiaotong University (China).


Poster

Poster Download poster (12.93 MB)

Abstract

Mesh Sensitivity Tests and Model Validation in Complex Sites in Southern China

Introduction

With the rapid expansion of the Chinese wind industry, one of the biggest challenges for wind resource specialists is to do reduce project uncertainties with limited measurement data availability. Less data often means fewer meteorological towers per number of MW (Megawatts) and it makes accurate extrapolation (horizontal and / or vertical) of wind speeds from met towers to turbines more challenging. Because estimation of wind speeds across project sites continues to be one of the highest pre-construction energy estimate uncertainty, the topic deserves considerable attention and recent developments in wind modeling are investigated on complex sites in Southern China operated by Guangdong Province Wind Power Generation Co., Ltd.

Approach

Guangdong Province Wind Power Generation Co., Ltd worked on studying the Atmospheric Flows over several sites in China. Mesh sensitivity analysis and wind flow computations were performed with the CFD (Computational Fluid Dynamics) tool ZephyCFD® which uses the scalable OpenFOAM® solver.

Main body of abstract

Thanks to lower cost of computational power and recent improvement in simulations convergence behavior, CFD simulations can now be based on unstructured meshes. This meshing technique uses prismatic cells instead of tetrahedrons and is considered to be more challenging to be generated than traditional structured meshes. However, unstructured meshes has several advantages for increasing simulations efficiency. Indeed, a single mesh can be generated for the whole wind rose simulations over a cylindrical computation domain and the use of prismatic cells enable generating heterogeneous refinements zones which allows reducing time without affecting accuracy by reducing the number of cells. For each of the sites of this analysis, five different meshes were tested to analyze the sensitivity of the horizontal discretization parameters, the vertical discretization parameters and the smoothing parameters of the meshes on the final output quality.

Conclusion

In complex sites, simulation accuracy seems to be more sensitive to vertical discretization parameters. The horizontal discretization being less sensitive, it is recommended to use heterogeneous refinement to control the number of cells (i.e. the calculation duration) without affecting the quality of the simulations.


Learning objectives
1/ Unstructured meshing techniques can improve the quality of CFD simulations
2/ Heterogeneous refinement for the horizontal discretizaton increases simulations efficiency
3/ Simulation quality is very sensitive to vertical discretization parameters in complex sites