The intake pool of a deep-tunnel pump station is highly prone to air-entraining vortices due to its unique structural design, which can significantly impair pump performance. However, the mechanisms behind the initiation, development, and interaction of vortices in this specific intake pool configuration are not well understood. The lattice Boltzmann method combined with large-eddy simulation (LBM-LES) has been demonstrated in other fluid dynamics areas to match the accuracy of traditional LES methods while providing benefits in boundary handling and parallel processing. To examine vortex characteristics in the intake pool of a deep-tunnel pump station, this study uses the LBM-LES approach along with particle image velocimetry (PIV) flow-field measurements and numerical simulations on a model of the pump station. By comparing experimental data with simulation results, the study verifies the reliability and precision of the LBM-LES method. The combined experimental and numerical findings are then used to analyze vortex distribution and flow-field features of the intake pool under various operating conditions.

A 10∶1 scale model of the deep-tunnel pump station intake pool was built in this study. To analyze the development of air-entraining vortices, three operating conditions— "below the critical Reynolds number Re," "at the critical Re," and "above the critical Re" —were set for the experiments and simulations, all using the same water depth. PIV flow-field measurements were then performed under these conditions, and vortex evolution of the scaled model was simulated with the LBM–LES method. The numerical results from LBM-LES were validated by comparing the average velocities and velocity components along measurement lines in both the simulations and experiments. Finally, the experimental and numerical data were used to examine vortex characteristics across different sections of the intake pool, including vortex distribution, intensity, and scale. By comparing vortex features under various operating conditions, the evolution of vortices near the critical condition was determined.

The numerical and experimental results showed the following: 1) The LBM-LES model aligned well with the experimental data. The velocity-component errors at key measurement points were within 5%, and the predicted number, distribution, and vorticity strength of the vortex structures matched the experimental observations. 2) The flow above the right outlet pipe was affected by multiple vortex systems. As Re increased, the vortex system near the right wall tended to merge, the vortex structures became more stable, and the vorticity gradually intensified. The flow above the left outlet pipe was dominated by a single vortex. With increasing Re, this vortex shifted from the left wall to a position directly above the pipe near the rear wall, and its vorticity progressively increased. Meanwhile, numerous vortices with opposite rotational directions formed around the main vortex system and extended toward the left and right walls of the intake-pool expansion section. 3) Vortices tended to form above outlet pipes near the rear wall. As Re increased, the negative vorticity above the pipe in Section 1 increased, while the vortex structure above the pipe in Section 2 moved closer to the free surface, and its vorticity gradually increased.

The LBM–LES method was verified as a reliable and accurate approach for simulating vortex evolution in the intake pool of a deep-tunnel pump station, providing a new mesoscopic tool for similar intake-flow studies. Meanwhile, the investigated vortex characteristics will deepen the understanding of the vortex formation mechanism in this special type of intake pool, offering valuable engineering guidance for optimizing its structural design.