dc.contributor.advisor |
Archer, R |
en |
dc.contributor.advisor |
Flay, R |
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dc.contributor.author |
O'Sullivan, John |
en |
dc.date.accessioned |
2012-08-14T21:34:55Z |
en |
dc.date.issued |
2012 |
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dc.identifier.uri |
http://hdl.handle.net/2292/19443 |
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dc.description.abstract |
The increasing worldwide use of wind energy means that wind farms are being constructed in areas where the terrain is complex. Two important features of wind flow over complex terrain are flow separation and anisotropic turbulence. The most commonly used simulation approaches for wind flow use either linearised methods or the Reynolds-averaged Navier-Stokes (RANS) equations with a k-ε turbulence closure. Neither of these approaches are capable of estimating separation accurately and they cannot represent anisotropic turbulence. In the research discussed in this thesis an effective and robust approach for modelling wind flow over complex terrain was developed using two accurate turbulence closures capable of capturing these features. One is the v²f turbulence closure which has shown good ability to predict flow separation in other applications. The other is the algebraic structure-based turbulence model (ASBM) which can accurately represent anisotropic turbulence. A new algorithm for blending a full Reynolds stress tensor turbulence closure with an eddy-viscosity closure is presented. It blends the v²f and ASBM closures enabling stable simulations of a number two-dimensional and three-dimensional flows. By gradually increasing the blending factor results are obtained for the ASBM closure alone. Estimates of the wall-normal fluctuations and the Reynolds stress components adjacent to the ground were required to extend the v²f and ASBM closures to simulations of wind flow over complex terrain. Using a combination of fundamental physics and previously published results new wall functions were developed that provided these estimates for both smooth surfaces and rough terrain. The same scalings were applied for key parameters as are used in existing standard wall functions to ensure that new wall functions are consistent. The new wall functions were validated using a number of test cases and are shown to be robust and accurate. An investigation of boundary conditions is carried out and a method is presented for generating realistic wind profiles for the inflow boundary of wind flow simulations. Combining these techniques simulations are carried out of two-dimensional flows over smooth and rough representative hills and of three-dimensional flows over real hills. Comparisons are made with experimental data and previously published simulation results. For the two-dimensional simulations over a smooth hill the results show that the ASBM closure accurately estimates the mean flow and turbulence and outperforms simulations using other closures. For the rough hill the ASBM closure combined with the new wall functions achieves a very good agreement with the experimental data and accurately represents the anisotropic turbulence. The three-dimensional simulations of the wind-tunnel experiments of Kettles hill confirm the effectiveness of the approach. The results obtained for the profiles of both the mean wind velocity and the components of the Reynolds stress tensor provide a good match to the experimental data. The full-scale simulations of Askervein hill are the first application of the ASBM closure to a high Reynolds number, three-dimensional, atmospheric flow. The comparisons with field data show that the approach presented in this thesis produces accurate estimates of the wind flow over complex terrain. For the steady parts of the flow the ASBM closure performs as well as or better than previously published solutions obtained using large-eddy simulation (LES) and hybrid RANS/LES. The success of the approach presented in this thesis for accurately modelling wind flow over complex terrain on the scale of a wind farm makes it a very useful tool. It is envisaged that it will be adopted more widely and more validation of the ASBM closure and the new wall functions will occur. |
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dc.publisher |
ResearchSpace@Auckland |
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dc.relation.ispartof |
PhD Thesis - University of Auckland |
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dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. |
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dc.rights.uri |
https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm |
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dc.rights.uri |
http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ |
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dc.title |
Modelling Wind Flow Over Complex Terrain |
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dc.type |
Thesis |
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thesis.degree.grantor |
The University of Auckland |
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thesis.degree.level |
Doctoral |
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thesis.degree.name |
PhD |
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dc.rights.holder |
Copyright: The author |
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pubs.author-url |
http://hdl.handle.net/2292/19443 |
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pubs.elements-id |
345216 |
en |
pubs.org-id |
Engineering |
en |
pubs.org-id |
Engineering Science |
en |
pubs.record-created-at-source-date |
2012-05-01 |
en |
dc.identifier.wikidata |
Q111963537 |
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