Gas–liquid flow characteristics of spiral separators with different downward bevel angles

The spiral separator is an efficient gravity separation device widely used in mineral processing because of its environmental friendliness and low maintenance requirements. The downward bevel angle is a key structural parameter of the spiral separator. However, its impact mechanism on multiphase flow characteristics and separation performance remains unclear. This study employs the volume of fluid multiphase flow model and the Renormalization Group k–ε turbulence model to conduct numerical simulations on spiral separators with four different downward bevel angles. The results show that the flow film thickness gradually increases from the inner to the outer trough. The tangential velocity positively correlates with water depth and radial distance. The secondary flow is more concentrated in the outer trough and exhibits turbulent flow, while it is weaker and laminar flow in the inner trough. As the downward bevel angle increases, the flow film thickness in the inner and middle troughs increases, which is beneficial for enhancing the tangential velocity at the same position. Conversely, a thinner flow film in the outer trough reduces the tangential velocity at the same position. The overall scope and intensity of the secondary flow increase, which expands its range inward and effectively facilitates the inward aggregation of the concentrate. However, this also reduces the laminar flow range in the inner trough, which decreases the stability of the flow within the concentrate band. Additionally, the expansion of the secondary flow range increases the turbulent flow range, making fine-grained heavy minerals easier to separate from the tailings and enhancing their tendency to move inward.