A comprehensive numerical analysis of the fluid flow and dilute particulate flow in the LD9 spiral separator is presented in this work. The air–water flow field on a coal spiral is simulated using the volume of fluid (VOF) coupled with RANS turbulence models. Water depth and flow field predictions by RSM show close agreement with experiments. Stability depth, turbulence intensity was analyzed for entire liquid depths. The discrete phase model is used to model the dilute particulates at different flow rates. Turbulent dispersion of particles using dispersion index and Bagnold force analysis indicate that centrifugal force dominates the separation at increased particle size and water depth level, whereas the fines are significantly affected by turbulence dispersion at the outer trough region. The magnitude of the Bagnold to gravitational force increases from the inner to outer trough region and a dip at the outer edge region due to inherent change of shear rate. Coarse particles experience higher lift than the fines and migrate to the top flowing layers. © 2022 Elsevier Ltd