Date of Award
Doctor of Philosophy
The complex turbulent flow in the wake of single isolated structures presents a formidable challenge to current modelling techniques. Models ranging from similarity based analytical models to fully numerical solutions of the flow have evolved to tackle this intriguing flow. Models also exist to predict the effect of the wake on the dispersion of contaminants entrapped by it. Such predictions are essential to public health and safety. In the industrial world, however, structures affecting the dispersion of contaminants are rarely single and isolated. More commonly, such buildings are located in small groups or clusters. To this end, this study examines the effectiveness of using single structure theory to predict the turbulent flow and the dispersion of contaminants in the wake of multiple structures located in a group.;A comprehensive study of turbulent flows and contaminant dispersion was conducted in an 'open county' type atmospheric boundary layer flow, using cross wire anemometers and flame ionization detectors. The primary structure groups studied consisted of a single row of three cubes of various clear separating distance. The separation distances examined range from closely packed to nearly isolated. Limited tests on non-cubic structures and double row arrangements were also conducted to round out the study.;The mean velocity deficits in the far wake of multiple structures are shown to coalesce into a single uni-modal wake. The combined wake is then demonstrated to decay in a universal manner when scaled by the overall width of the structure group. The single structure similarity theory of J. C. Hunt is subsequently modified and successfully applied to multiple structure wakes in this region of universal decay.;A Modified Area Source model is developed to predict mean contaminant concentrations in the wake of multiple structures. The model uses the universal decay feature of the mean velocity deficit in the wake to modify the advection velocity of the contaminant. Universal functions are also developed to describe measured turbulent velocities. These functions are used to modify the turbulent spread parameters of the model. Predictions made by these modifications represent significant improvement over previous models, most of which incorporate arbitrary constants to fit the data.
Musselman, Daryl Douglas, "Turbulent Wake Interactions Of Multiple Structures In An Atmospheric Boundary Layer" (1996). Digitized Theses. 2654.