Author(s): R. Iasenza; S. Babarutsi
Linked Author(s): Sofia Babarutsi
Keywords: Rectangular Basins; Mixing; Velocity Field; Turbulence; Measurements; Hot-Film Anemometry; Artificial Aeration; Flow Visualization; Hydraulics
Abstract: The hydraulic behavior and mixing processes in rectangular basins are studied experimentally in a laboratory scale model. The laboratory basin was modeled after a full scale aerated lagoon operating in Saint-Julie, Canada. Two sets of experiments were conducted: one without artificial aeration and the other using a large bubble diffuser. For both sets, two-dimensional mean and root mean square velocities were measured using a hot-film anemometer. Further, a flow visualization technique was used as a qualitative approach. The results show that the hydraulic behavior of non-aerated rectangular basins is very complex, due to the formation of flow patterns such as stagnant zones and recirculation. The location and size of these flow patterns are determined using the measured velocity flow field and the flow visualization. Mixing in these basins is highly non-uniform, since flow is clearly segregated into high-velocity and lowvelocity areas. The exchange between these areas is very low, affecting the distribution of solids and contaminants. When large bubble aeration is introduced, mixing becomes more uniform, as the size of stagnant zones and the extent of recirculation decreases. For the tests studied, aeration increases mixing predominantly in the lateral direction. Also, aerator position and flowrate are identified as important parameters which influence mixing. The understanding of mixing and transport mechanisms in rectangular basins is important, because such basins are often used in applications which require settling or mixing of solids and contaminants.
Year: 1999