Multiphase Transport Help

nm

Hi, I m using fluent to run multiphase simulations of cutting transport. Basically I have an annular section through which a fluid and solids flow through. Now, I unsure about the procedures involved. Some of my particles are goin to get trapped inside the domain and not exit with the fluid. But I cant seem to get a change in concentrations between the outlet and inlet of the second phase(solid). I m using the mixture model. My boundary conditions are velocity inlet and outflow at the 2 ends of the annulus