Factors influencing the removal of fine non-cohesive sediment by vortex settling basin at small river abstraction works |
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| Authors: | Kuria Kiringu Gerrit Basson |
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| Institution: | Department of Civil Engineering, University of Stellenbosch, Stellenbosch, South Africa |
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| Abstract: | Diverted sediment causes a wide range of problems at small diversion works. The difference in water levels between low flows and floods, low investment capital and presence of cohesive sediment and fine non-cohesive sediment coupled with a requirement for a high level of supply assurance makes the design of such hydraulic structures complex. Vortex settling basins (VSBs) offer a promising alternative to conventional settling structures or hydro-cyclones. In the current study, parameters affecting the trapping of particles >75 μm were numerically investigated using ANSYS Fluent and were validated by physical modeling. It was established that the inlet velocity needs to be maintained at 0.26 m/s, the underflow to inflow ratio should be between 0.05 and 0.10, the cylinder height to cylinder diameter ratio should be greater than 0.5, and the positioning of the inlet pipe to cylinder height ratio should be greater than 0.7, with a cone of slope ratio of 2:1 (V:H) and the cylinder diameter to inlet diameter ratio should be 8.2. These parameters form the basic design guidelines for VSB use at small diversion works (<100 L/s duty capacity). |
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| Keywords: | Vortex settling basin Sediment trapping efficiency River diversion works ANSYS Fluent Numerical modeling |
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