针对新型低品位铝土矿湿法提质工艺中尾渣与铝精矿复杂嵌布导致的铝精矿收率和品位降低问题，基于?75 mm旋流器中试平台，采用计算流体力学模拟与实验验证相结合的方法，以底流口直径(4, 6, 8, 10和12 mm)为唯一变量，探究其对旋流器内部流场及分离性能的调控机制，明晰湍流动能分布与流场稳定性的作用机理。模拟结果表明，通过改变底流口直径可有效调控湍流动能大小及分布，结合流场特性阐明了短路流和循环流的演变趋势，强化尾渣与铝精矿的高效解离。实验结果表明，进料压力为0.3 MPa、进料质量浓度为17.15wt%、进料铝硅比为2.74时，8 mm底流口对流场的稳定与分离性能有显著提升，抑制溢流跑粗和底流夹细现象，解决了铝精矿收率低、品位差的问题，与原始旋流器相比，精矿产率提高9.33%，铝硅比提升20.39%，且模拟结果与实验数据高度一致。研究结果可为复杂矿浆体系旋流器的结构优化提供理论依据，对工业级低品位铝土矿资源高效回收具有指导意义。

Tailings produced by the novel wet beneficiation process for low-grade bauxite exhibit complex morphological characteristics and intricate occurrence states, posing significant challenges for efficient aluminum concentrate recovery. These complexities result in reduced recovery rates and lower concentrate grades. To address this issue, this study systematically investigates the effects of underflow orifice diameter (4, 6, 8, 10, 12 mm) on the internal flow dynamics and separation efficiency of a hydrocyclone. A pilot-scale ?75 mm hydrocyclone system was employed, with the underflow orifice diameter as the sole variable while maintaining other structural and operational parameters constant. Computational fluid dynamics (CFD) simulations, combined with experimental validation, were used to explore how variations in underflow orifice diameter influence turbulent kinetic energy (TKE) distribution and flow field stability, ultimately affecting the efficiency of tailings-aluminum concentrate separation. Simulation results indicated that adjusting the underflow orifice diameter significantly regulated the magnitude and spatial distribution of TKE, which in turn governed the evolution of short-circuit flow and recirculation flow within the hydrocyclone. An optimal balance was observed at underflow orifice diameter of 8 mm, which effectively stabilized the internal flow field, controlled short-circuit and recirculation flow, and enhanced the dissociation of tailings from aluminum concentrate. Experimental results, conducted under feed pressure of 0.3 MPa, feed concentration of 17.15wt%, and an alumina-to-silica mass ratio (A/S) of 2.74, confirmed that the optimized 8 mm underflow orifice hydrocyclone significantly improved separation performance. Compared to the baseline design, the 8 mm orifice increased underflow concentrate yield by 9.33% and improved the A/S ratio by 20.39%, effectively mitigating coarse particle overflow and fine particle entrainment. Strong agreement between CFD simulations and experimental data validated the reliability of the numerical approach. The findings provide a theoretical framework for optimizing hydrocyclone designs in complex slurry separation processes, particularly for low-grade bauxite beneficiation. By elucidating the interplay between TKE modulation and flow structure evolution, this study offers valuable insights for industrial applications, contributing to the development of more efficient hydrocyclone separation strategies.