抄録
Settling basin is an essential need, when river water is withdrawn from middle-high water flow in which water is highly turbid. A novel fan-shaped settling basin is tested and the hydraulic structure in the basin is investigated by hydraulic model experiments. A radius of the fan-shaped basin model is 320 cm and a central angle is 30 °. Both a submerged weir and a submerged rectangular orifice are installed in the upper stream of the basin to rectify the inflow. Measured discharge coefficients of the weir and the orifice are very similar to the conventional values. Wake region in the basin, where a counter flow is seen in the upper layer and a jet in the lower layer, expands to the distance of 100-140 cm from the orifice, which is roughly equal to 10 times as large as the depth of the orifice upper edge. Coefficient of variation is introduced to evaluate the non-uniformity of the flow in vertical transversal planes of the basin. Using the coefficient of variation, the difference in the variation of flow between the wake region and the other region is quantitatively evaluated.
