Analysis and improvement of hydraulic characteristics of step energy dissipators in double-layer pumping stations for urban sewage lifting

To improve the hydraulic flow pattern and energy dissipation rate of the step energy dissipator in the double-layer pumping station for urban sewage lifting and reduce the impact on the step surface, based on the numerical simulation method, the renormalization group (RNG) k-ε turbulence model and the volume of fluid (VOF) model were used to analyze the hydraulic characteristics of the step energy dissipator. There are adverse flow patterns of the mainstream being biased to the right and “water wings” in the water flow of the step energy dissipator. To address this issue, a combined rectification optimization scheme of “diversion ramp + diversion pier + tail ramp of steps” was proposed, and its optimization effect was analyzed. The results show that the diversion ramp can effectively increase the flow on the left side of the step and improve the adverse flow pattern of the deflected flow. The diversion piers and the tail piers of the steps can reduce and homogenize the axial velocity of the water flow at the exit section of the steps and suppress the formation of “water wings”. Under the design flow conditions of the pumping station, the uniformity of the total flow distribution of the first step of the combined step energy dissipator has increased by 0.42; the maximum pressure on the left side of the horizontal plane has decreased by 17%; the maximum pressure on the right side has decreased by 21%, and the energy dissipation rate of the combined step energy dissipator has increased by 4.12%.