Vortex‐Settling Basin Design Considerations

Abstract

The vortex‐settling basin (VSB) is a fluidic device that uses only the vortices of the flow to remove sediment. This is an economical, efficient, and water‐conserving alternative to the other available sediment‐extraction devices. This paper presents guidelines for designing and modeling VSBs. It shows that the circular basin should have diameter equal to five times (as compared with six times stipulated in American practice) the bed width of inlet canal. The distinctive features of the proposed design are formation of free vortex in the outer region and flow in the basin traversing a relatively longer path before reaching the overflow weir. Extraction of sediment smaller than 0.5 mm is optimized when a diaphragm and a deflector are incorporated in the inlet canal and basin, respectively. Diameter of the flushing pipe and the flushing discharge to be adopted for the extraction of different sediment fractions are specified. Formulas suggested for prediction of trapping efficiency are simpler and more reliable than several existing formulas. Experiments indicate 76% utilization of the VSB volume and, therefore, show a better performance compared to standard sediment tanks.