Combined-sewer-overflow (CSO) reservoirs are being built by the Metropolitan Water Reclamation District of Greater Chicago as part of the Tunnel and Reservoir Plan. A significant load of organic material and inorganic suspended sediment are expected in the inflow to the reservoirs. A primary concern is that sediments will settle out and remain on the bottom of the reservoir after de-watering. One design being considered is to use air diffusers to create bubble-plumes to keep the contents of the reservoir aerated, mixed and the sediments in suspension until it can be pumped out and treated. To quantify the amount of mixing that would be needed to keep the sediment in suspension, the characterization of the flow turbulence induced by bubble-plumes in combined-sewer-overflows is required. The present work provides a detailed set of experimental data quantifying the flow turbulence and mixing induced by bubble-plumes in large experimental facilities with combined-sewer-overflows under non-stratified conditions.; To provide a consistent set of experimental data several issues were addressed in this thesis. First, the acoustic Doppler velocimeter technique was selected as the optimum technique to accurately characterize the flow turbulence induced by bubble-plumes in large facilities with presence of combined-sewer-overflow. The turbulence characterization was performed on basis of data recorded in an intermediate region of the tank away from the plume, water surface, walls, and bottom with a homogenous behavior of the turbulence parameters. Different scale-dependent turbulence processes induced by bubble-plumes in large facilities were identified and their contributions to the turbulence parameters were quantified.; An analysis of the effects of the different experimental conditions on the observed turbulence parameters allowed identifying the main variables (tank geometry, water depth, and air discharge) controlling the induced mixing in the tank. Finally, the extensive set of experimental data was summarized in a set of dimensionless plots which can be used to conduct a preliminary design of coarse-bubble diffuser for reservoir mixing and to validate numerical models of bubble-plume systems used in the design of the combined-sewer-overflow reservoirs.
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