In contrast to the concurrent mixer-settler

the interaction between the mixing and settling chambers have to be taken into account in the simulation of the countercurrent mixer-settler

and no work has been reported for this equipment. In this work

a three-phase flow model based on the Eulerian multiphase model

coupled with a sliding mesh model is proposed for a countercurrent mixer-settler. Based on this

the dispersed phase distribution

flow pattern

and pressure distribution are investigated

which can help to fill the gap in the operation mechanism. In addition

the velocity vector distribution at the phase port shows an intriguing phenomenon that two types of vectors with opposite directions are distributed on the left and right sides of the same plane

which indicates that the material exchange in the mixing and settling chambers is simultaneous. Analysis of this variation at this location by a fast Fourier transform (FFT) method reveals that it is mainly influenced by the mixing chamber and is consistent with the main period of the outlet flow fluctuations. Therefore

by monitoring the fluctuation of the outlet flow and then analyzing it by the FFT method

the state of the whole tank can be determined

which makes it promising for the design of control systems for countercurrent mixer-settlers.