Flow Field Investigation in a Vortex Settling Basin Using Acoustic Doppler Velocimetry and Large Eddy Simulation

Vortex settling basin is an efficient continuous flushing system to remove the sediment in water and wastewater treatment plants. In the current study, computational fluid dynamics was implemented to study sophisticated flow field within the Vortex settling basin. The performance of 3-D Reynolds-averaged Navier-Stokes turbulence models including standard k-epsilon and SST k-omega models and a large eddy simulation, Smagorinsky model, were assessed. The 3-D velocity field was also measured using Acoustic Doppler Velocimetry. The effects of vortex generation on basin performance and flow properties in the VSB were analysed. Secondary currents were identified as important phenomena in settling and flushing of sediment particles through the bottom orifice. The experimental data were used to evaluate the accuracy of the calculated flow field. The results of the numerical simulation confirmed the superiority of the Smagorinsky model. This model satisfactorily simulated the water surface and the overall pattern of secondary currents in the VSB.