This study reports the development and validation of a modified two-equation eddy-viscosity turbulence model for computational fluid dynamics prediction of transitional and turbulent flows. The existing terms of the standard k-w model have been modified to include transitional flow effects, within the framework of Reynolds-averaged, eddy-viscosity turbulence modeling. The new model has been implemented into the commercially available flow solver FLUENT and the Mississippi State University SimCenter developed flow solver U2NCLE. Test cases included flow over a flat plate, a 2-D circular cylinder in a crossflow, a 3-D cylindrical body and three conical geometries, which represent the nose-cones of aerodynamic vehicles such as missiles. The results illustrate the ability of the model to yield reasonable predictions of transitional flow behavior using a simple modeling framework, including an appropriate response to freestream turbulence quantities, boundary-layer separation, and angle of attack.

Tropical cyclones in the Atlantic basin often undergo a process called extratropical transition (ET) and transform from warm-core to cold-core systems while retaining strong winds, heavy rainfall, and large ocean waves. Infrared satellite imagery from channels 2 and 4 of the Geostationary Operational Environmental Satellite (GOES) were used to examine key structural changes, synoptic interactions, and loss of deep centered convection in order to determine onset and completion of ET. The primary indicator for ET onset in 75% of cases was found to be a persistent increase in storm asymmetry along with the appearance of warm frontogenesis in its northern region. Cold frontogenesis in the southern portion of the storm was the secondary indicator for declaring onset of ET. Completion of ET was marked by the loss of centered deep convection for all cases. The average ET transition time was 18 hours for 60% of the cases.

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This dissertation takes the opportunity to explore an existing building in need of change owing to changing environments. The proposed project is situated within the city context of Pretoria and aims to address the unavoidable nature of architecture, which involves the degradation of buildings over time. The main focus of this study is the concept of waiting, where the city dweller has to endure spending time in everyday surroundings in a built environment. The study attempts to understand the deeper psychological meaning of waiting better in order to provide places that are sympathetic to the waiting person. The aim of this dissertation is to justify the importance of the waiting place and to investigate waiting places in everyday environments, in order to determine physical factors that influence the experience of people while waiting. These factors inform decisions to provide improved facilities within an informal transport system, while generating new functions in response to the behaviour of people in a transit environment. The principles of waiting are exploited to create an environment where the building acts as generator for new infill parts to serve the user. The project envisages a fresh approach to reunite the waiting place and architecture to create a social gathering space. The project’s main goal is to consider the waiting space as one that serves as a transition place for travellers, providing the commuter with the opportunity to orientate and recover from tiring daily activities. The proposed project addresses the needs of the city dweller by means of a renewed building intervention. The changing context required a site related function that serves the user and acts as a support system in the city, facilitating future growth. / Dissertation (MInt(Prof))--University of Pretoria, 2010. / Architecture / unrestricted

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