Author(s): Arash Farjood; Bruce W. Melville; Asaad Y. Shamseldin; Nickvigar
Keywords: Hydraulic efficiency; Tracer study; Sediment retention pond; Inlet and outlet; Baffles
Abstract: This study addresses the effect of different inlet and outlet configurationsand the influence of baffles on the hydraulic performance of a model pond. The physical model is a trapezoidal pond with top dimensions of 4. 1 × 1. 6 m × 0. 3 m deep and side and end slopes of 2: 1. For simulating the sediment forebay, the inlet pipe fills a rectangular tank of 0. 3 × 1. 6 × 0. 2 m. For dewatering the pond, three perforated T-bars are fixed to an outlet riser to simulate a floating decant dewatering system. Tracer experiments were carried out using Rhodamine-WT fluorescent dye to obtain residence time distribution (RTD) curves and subsequently assess the hydraulic efficiency. Solid and partial-width baffles were also investigated for their influence on the hydraulic efficiency of the system. Compared with the conventional point inlet and outlet system, the results herein showed that distributing the inflow over the entire width of the pond could successfully improve the hydraulic efficiency, albeit with short circuiting along the sloping side walls. Monitoring the dye aided recognition of preferential flow paths which were subsequently removed by modifying the inlet. On the other hand, the outlet span was adjusted to boost the residence times. Hydraulic efficiencies of about 0. 50 compared with 0. 18 for the conventional system, illustrated the effectiveness of these configurations. Furthermore, both types of the tested baffles significantly lifted the hydraulic performance giving the highest hydraulic indices of all the tested cases. These results indicated the need for experimental investigation of such systems for an improved understanding of their hydraulic performance.