Abstract: With the process of production， the wall roughness of spirals is not quantitative and very complex， if it is not properly controlled， the material separation effect will be seriously affected. Based on the previously established spiral flow field model and particle phase computational model， the influence of the wall roughness on the slurry flow of hematite and quartz and particle separation behaviors in 400mm spirals was systematically investigated. The simulation results show that the slurry depth， Reynolds number， and flow velocity have notable differences in radial distribution and fluctuation characteristics. With the increase of roughness， the separation fluid space significantly contracts when the roughness height reaches 0.1mm or higher. the range of laminar flow distribution expands， while the transition flow range narrows. The velocity values exhibit a clear correlation with the roughness. Higher roughness intensifies the fluctuation of the main flow and the inner circulation， leading to noticeable disruption of the inner circulation. For roughness height below 0.1mm， increasing the roughness facilitates the convergence of coarse hematite towards the inner margin， maintaining a high separation efficiency for coarse hematite and fine quartz. However， the separation efficiency decreases significantly with the further increase of roughness. The increase of roughness intensifies the distribution of fine hematite in the middle and outer regions， resulting in a substantial decrease in the separation efficiency of fine hematite and quartz. The change of particle separation behaviors is closely related to the change of flow field characteristics.

Key words: wall roughness; spirals; slurry flow; product segmentation; separation efficiency