Nowadays, the wind energy industry employs different types of turbulence models which are capable of reproducing the correct and realistic behaviour of relatively simple flows (e.g. Wind over flat, homogeneous and obstacle free terrain). However, as the complexity of the flow increases (e.g. wind over complex topography), the accuracy of the turbulence models may be greatly reduced, and in general, their computational cost rises significantly. Accurate and reliable flow simulations are still not practical for wind industry applications over complex terrain.
To improve wind flow simulations over complex terrain, two of the main challenges that the wind energy sector faces are addressed. The first challenge is related to the fact that ground surface modelling treatments are valid only on flat terrain. Nevertheless, it is a common practice to use those surface treatments on simulations over complex terrain. However, the k − ω SST (shear stress transport) turbulence model has a novel surface treatment that is less dépendent on flat terrain assumptions. The second challenge is the high computational cost when accuracy and reliable turbulence statistics are needed. Nonetheless hybrid turbulence models could provide a good compromise between accuracy and computational cost. A turbulence model based on the k − ω SST model and the simplified improved delayed detached-eddy simulation (SIDDES) hybrid technique is proposed to address those needs.
To validate this model for atmospheric flows, first an extensive analysis of certain canonical flows was carried out. This rigorous validation helped understand the inherent limitations of the turbulence model within the specific numerical framework. Subsequently, computations of the neutrally stratified atmospheric flow over flat homogeneous terrain and then over complex topography were conducted. The results show that the k − ω SST-SIDDES turbulence model is able to predict realistic wind behaviour over flat terrain and more complex cases. The vertical grid refinement in the near-wall region required by this model poses a major challenge for the mesh generator. But despite this limitation, k − ω SST-SIDDES turbulence model proved to be a suitable approach for modelling the wind flow over complex terrain without relying on flat terrain assumptions or requiring substantial computer resources.
| Date | 19 Oct 2015 |
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| Original language | American English |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Louis Dufresne (Supervisor) & Christian Masson (Co-supervisor) |
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Bautista, M. C. (Author),
Dufresne (Supervisor) & Masson (Co-supervisor),
19 Oct 2015Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering