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Browsing Office of Sustainability by Subject "CFD"

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    Computational Modelling of the Wind Flow over the University of Calgary Campus
    (2015-09-04) Mohamed, Mohamed; Wood, David
    This thesis investigates the issues pertaining to computational wind resource in the urban environment. The effect of trees on wind distortions above the roof of a 15-m high building was modelled via sink and source terms in the momentum, k and ɛ equations. The results from the simulations showed mean wind speed above the roof was not a monotonic function of ratio of tree-to-building height. Further, the trees reduced k over the roof via reduced production. Stagnating turbulent flows occur in an urban setting and the over-prediction of k with the standard k-ɛ turbulence model is ameliorated with a formulation of the eddy viscosity that eliminates the dependence of the production term on the components of the mean strain rate. The new turbulence model, MW, improved predictions for k over the roof of a simulated building. Its predictions for mean wind speed and k improved further with blending functions. The MW was tested on flows over a rough 2D ridge and a 3D hill and compared with the SST and k-ɛ . The MW showed good predictions for k relative to experiments at the crest of the 3D hill and also portrayed a feature that does not allow the flow to relax too quickly downstream of the 3D hill unlike the SST and k-ɛ. The behaviour of simple RANS models along a stagnation streamline of a normal at plate in a wind tunnel were compared with experiments. All models over-predicted k and the important terms in the k budget while large changes to k do not affect the mean velocities. The most accurate of the models was the ω-based Reynolds stress model. A simulation of the wind flow over the University of Calgary campus was undertaken to assess the likely regions for siting wind turbines and photovoltaic modules. The effect of the terrain and the many trees on the campus is shown to be significant for the wind resource over the roof of a six-storey building. The choice of turbulence models is not critical if the purpose of the simulations is to identify regions for further exploration via wind speed measurements.