This study presents a mathematical model to predict water-flow characteristics, especially primary (downstream) and secondary velocities on the spiral trough. The study is based on volume of Fluid (VOF) approach and turbulence modeling. The applied turbulence models are kε, RNG k-ε, SST k-ω, and RSM. The results show that the primary velocity increases on the spiral trough with increasing of the radial distance from central column, and the air friction with the water decreases the primary velocity at the free surface. The model is validated against experimental data from LD9 coal spiral. Comparisons between the predicted and the measured values show good agreements, and the RSM is the most accurate turbulence model while the SST k-ω model is the lowest accuracy.