Unfavorable flow patterns, such as vortices and backflow in pump station forebays, can deteriorate pump suction conditions and exacerbate sediment deposition. This study investigates the effects of different pump unit operation combinations on the flow patterns in the forward-intake forebay of the Hongsi Pumping Station. A three-dimensional numerical model was established using the RNG k-ε turbulence model combined with the VOF method for free surface tracking, with Enhanced Wall Treatment employed for the near-wall region. The model was validated against field measurements, with mean absolute errors of 0.058 and 0.085 for two characteristic lines, respectively. Four unit operation combination schemes were simulated and compared. Results show that the velocity in the front end of the main flow zone reaches 0.344–0.345 m/s across all schemes, which is 19–24% higher than in the middle section and 26–37% higher than in the rear section. The inter-scheme velocity variation is minimal near the forebay inlet (1.1% at section X1) but increases significantly near the pump inlets (approximately 11% at section X4), indicating that unit operation combinations primarily affect the rear forebay region. Large-scale vortices are observed near the side walls and pump inlets, with vortex cores located at different positions depending on the operation scheme. When the units at both ends are operated symmetrically (Scheme 1: units 1#, 2#, 5#, 6#), the flow pattern is the most favorable, displaying characteristic dual-core vorticity distribution with symmetric pattern and moderate intensity, with the velocity uniformity at the inlet section reaching 81.77%, which is 5.21, 11.35, and 1.91 percentage points higher than Schemes 2, 3, and 4, respectively. For practical operation, Scheme 4 (1#, 2#, 4#, 5#) can serve as an alternative with a velocity uniformity of 79.86%, while central concentration and single-side bias configurations should be avoided due to their larger vortex scales and lower velocity uniformity. The findings provide quantitative guidance for the operation management of forward-intake pump stations.
Li et al. (Tue,) studied this question.