Flow Energy Dissipation in Vortex Drop Shaft by Tangential Inlet

Vortex drop shafts, with a primary function of dissipating flow energy, are used to transfer flow from higher to lower elevations. In the present research, the physical model of the vortex drop shaft of the eastern Tehran sewage system in Iran are studied and the effects of the inflow Froude number, inlet bottom slope, and the ratio of sump depth to vertical shaft diameter on the flow energy dissipation rate are surveyed. This study was performed with Froude numbers of 1.79, 2.01, 2.18 and 2.31, the inlet bottom slopes of 0.251, 0.4, and 0.571, and the sump depth to vertical shaft diameter ratios of 0, 1, and 2. Accordingly, 36 experiments were designed. For the purpose of increasing accuracy and analysis of results, each experiment is repeated 3 times. Consequently, 108 experiments were done. The results showed that the flow energy is dissipated  in the range of 93.7% to 98.5% by changing the parameters. In addition, increasing the inflow Froude number and the sump depth to vertical shaft diameter ratio cause the reduction of the flow energy dissipation rate in the vortex drop shaft by 2.2% and 3%, respectively. Also, increasing the inlet bottom slope increases the flow energy dissipation rate by 2.4%. According to the interaction between the flow energy dissipation and the outflow Froude number, the appropriate sump depth to vertical shaft diameter ratio proposed 0.3-1.2. Furthermore, a nonlinear relationship using the variance analysis was presented to estimate the flow energy dissipation rate.