Page - 193 - in Book of Full Papers - Symposium Hydro Engineering

noteworthy that S0 represents the no-vane mode. According to the results, with an increase in the radial sections of vanes, total efficiency reduced compared to the no-vane test S0 that among the three modes, minimum orifice efficiency was related to S8 and maximum orifice efficiency was related to S4. The results also show that with an increase in the radial sections of vanes, the orifice efficiency reduced in both discharges and the floor efficiency increased (lower sediment washing from the floor). Among S4, S6 and S8 modes, S4 has the best performance. Studying the effect of discharge on the vortex settling basin shows that discharge changes had little impact on the basin total efficiency but changed the share of settling in each part of the vortex settling basin. As seen in Figures 12 and 13, higher discharge (45 l/s) reduced the floor efficiency and increased the orifice efficiency. Lower discharge (37 l/s) reduced sediment washing from the floor. According to Figure 14, parameter G' was positive in R3 and R4 arrangements and both discharges but the reaction of these two arrangements was different in two discharges so that in the discharges of 37 and 45 l/s, R3 and R4 showed better reactions, respectively. R3 4 was somewhat successful in sediment washing from the floor but its value was less than R3 and R4 arrangements. As shown in Figure 14, the parameter G' was negative at discharges of 37 and 45 l/s for R4 and R3 4. This decline in sediment washing increased with radial sections of vanes (increased radial sections). Reduced sediment washing (G') at the discharge of 37 l/s occurred for all tests. The reason for reduced sediment washing of the floor at the lower discharge is the reduced vortex strength and the reduced speed because these basins have a better efficiency at high speeds. S0 when discharge is low, sediments are not affected by vortex flows within the basin and begin to settle on the basin floor. However, according to Figures 12 and 13, reduced orifice efficiency and reduced sediment washing on the basin floor also occur at lower discharges in no-vane modes. S0, in this type of basin, with an increase in discharge, vortex strength and thus vanes' efficiency in the basin will increase. Finally, the best cases of sediment removal from the floor occurred at the discharge of 45 l/s at the longitudinal distance of S4, and R3, R4 and R3 4 arrangements. The amounts of increase in sediment removal from the floor at the best cases for R3, R4 and R3 4 arrangements were 29.12%, 34.49% and 20.15%, respectively. Moreover, these arrangements increased the orifice efficiency in the discharge of 45 l/s by 13.66%, 15.73% and 4.26%, respectively. Finally This study first introduced previous research on vortex sediment basin and then provided a solution for a problem in vortex sediment basins which is the settlement of some percent of sediments on the basin floor and non-exit from the flushing orifice. The solution presented in this paper is to use curvature submerge vanes to increase vortex power and better conductivity of the floor sediments towards the flushing orifice. It was observed that after inserting curvature submerge vanes in the basin floor, with little change in total 193