Numerical Analysis of Flow Regulation Measures for Lateral Inflow Forebay of Submersible Pump Stations

[Objective] Lateral inflow of pump station can easily cause flow separation and backflow as the water body in the forebay changes direction, which deteriorates the flow pattern in the forebay and seriously threatens the efficient and stable operation of pump station units. [Methods] In this study, the computational fluid dynamics (CFD) method was used to calculate the flow field of the inflow building of Dazhaihe pump station, and the effectiveness of the numerical calculation method was verified by physical model tests. Quantitative and qualitative comparative analyses were conducted to evaluate the flow field characteristics of the forebay and the open inflow basin under five flow field regulation measures, including flow-guiding grille, flow-straightening sills, and different types of guide walls. [Results] (1) Based on the RNG k-ε turbulence model, the inflow conditions of lateral inflow forebay and inflow basin of the pump station in the initial design scheme were analyzed, and the effectiveness of numerical calculation method for the flow field in the pump station forebay was validated through hydraulic physical model tests. (2) The combination of arc and linear guide walls achieved optimal flow regulation effect. This measure facilitated the redistribution of flow velocity, reduced the non-uniformity of flow distribution across inflow basins, and stabilized lateral inflow. The area proportion of high-velocity zones at characteristic cross-sections was relatively small, and the average velocity along the horizontal centerline of this cross-section was slightly higher than theoretical cross-sectional average velocity. The velocity distribution within the inflow basin became more reasonable with reduced variability, significantly improving the overall flow field. (3) By comprehensively comparing five evaluation indicators—axial velocity distribution uniformity at the inlet of bell-mouth pipes in submersible pumps, the range of axial velocity distribution uniformity, velocity-weighted average angle, characteristic values of vorticity, and head loss coefficients between characteristic cross-sections—the combined application of arc and linear guide walls achieved optimal inflow conditions in the inflow basins of all units. Compared with the initial design scheme, the axial velocity distribution uniformity at the inlet surfaces of bell-mouth pipes in submersible pumps increased by 14.8% on average, and the velocity-weighted average angle increased by an average of 9.2°. Additionally, the range of axial velocity distribution uniformity between units was the smallest, and no vortex ropes were observed at the inlets of bell-mouth pipes in any unit. [Conclusions] The combined regulation measure using curved and linear guide walls is proven effective in mitigating the impact of adverse flow patterns on pump station units, providing reliable guidance for improving flow conditions in similar lateral inflow pump stations. For practical engineering applications, factors such as project timelines and construction complexity should be considered. The findings of this study offer feasible technical support and recommendations for the design and operation of future similar pump stations and hydraulic structures. Current research primarily focuses on flow field optimization of the lateral inflow forebay at the preliminary design stage, and further on-site testing of pump stations is required to evaluate the actual regulatory effects of the optimized schemes.