Date of Award

1991

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Civil and Environmental Engineering

Keywords

Engineering, Sanitary and Municipal.

Supervisor

McCorquodale, J. A.,

Rights

info:eu-repo/semantics/openAccess

Abstract

Density currents exist in most secondary sedimentation basins and cause the usual hydrodynamic flow patterns in these basins to deviate substantially from ideal condition flow patterns. In real tanks, the diurnal variations of inflow, temperature and concentration of suspended solids result in unsteady density currents. In this dissertation, the internal flow regimes associated with the density currents due to diurnal heat loading in radial sedimentation tanks are investigated. This study is restricted to currents due to an inflow which is denser than the ambient fluid in the tank. Experimental studies are made of the flow under different conditions of geometry, momentum and buoyancy. Velocity measurements of 90 tests at different flow regimes were determined. Temperatures at a large number of points at several sections along the tank radius were measured for a total of 66 tests. In addition, flow visualization dye tests were carried out. During the experiments, the phenomena progressed through a sequence of density flow regimes: (1) The denser radial wall jet; (2) The splash at the weir; (3) The travelling radial internal hydraulic jump; (4) The submerged internal hydraulic jump; (5) The splash at the gate; (6) Stratification. The temperature and photographic data are analyzed to determine the characteristic depths, velocities and temperatures of the radial denser wall jet and the sequent depths and surge velocities of the moving radial internal hydraulic jump. The velocity experiments showed a three layer velocity distribution. The occurrence of the shallow surface layer with positive horizontal velocity, and the increased bottom and recirculation velocities are distinguishing features of the present velocity measurements compared to those of neutral density flows. A numerical model was formulated to predict the flow characteristics associated with the radial denser wall jet. The jet depth, velocity and temperature were determined from the jet submodel while the sequent depth, surge velocity and the longitudinal position of the internal hydraulic jump were predicted by the moving internal hydraulic jump submodel. The model was verified by comparison with experimental data from the present study. The mathematical model is in fair agreement with the experimental data. This research can be used as a tool to verify proposed theories describing density currents in radial settling tanks.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1992 .M688. Source: Dissertation Abstracts International, Volume: 53-12, Section: B, page: 6524. Adviser: J. A. McCorquodale. Thesis (Ph.D.)--University of Windsor (Canada), 1991.

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