Page - 183 - in Book of Full Papers - Symposium Hydro Engineering

2 Experimental Equipment 2.1. Experimental Model Experimental studies in this research were done at a basin with a height of 96 cm and a diameter of cm. The flow direction in this basin was clockwise. This basin had a weir with a length of 168 cm. The diameter of the inlet opening of the flushing orifice of the vortex sediment basin is 59 mm. Sediments exiting from the basin flushing orifice are entered into a rectangular basin with dimensions of 2×1.5 m and a height of 0.5 m by a tube with a diameter of 17 cm for collection and analysis. Due to the turbulence caused by pumping water from the storage tank, it was necessary to reduce the flow turbulent before the flow enters into the vortex settling basin. So, at the beginning of the inlet channel, the flow smoothing basin was established with dimensions of 2.5  2.5 m and a depth of 2 m. The basin inlet channel had a length of 4 meters and a width 42.86 cm and a height of 71 cm. The vortex settling basin floor had a gradient of 0.1 towards the flushing orifice and also a deflector was installed below the weir, and a diaphragm was placed in the opening of the inlet channel. The deflector structure was installed in horizontal, flat and semicircular forms. To avoid leaving sediment particles on arrival at the basin influenced by the jet outflow, it was installed on top of the weir which increased residence time of the flow containing sediment within the basin and also sediments' spinning. The diaphragm was used in the settling basin to: a) improves the shape and conduction of the jet inflow to the basin; b) create vortex flow and increase the centrifugal force for the removal of suspended sediments in the vortex basin; c) increase the basin hydraulic efficiency and improve the core shape of central air (Keshavarzi and Gheisi 2006). At the downstream of the vortex settling basin, there were two channels; one for transporting passing water on top of the vortex basin weir and another for transporting the water of a rectangular settling basin after deposition of sediments, both of which had a width of 60 cm and a height of 60 cm. 183