[NAD]

hi. i tried to make fluidized bed simulation 2D.the geometry is simple:a cylinder 2D with inlet and outlet. BC are defined as flow:
Inlet at the bed bottom is designated as Velocity Inlet boundary conditions for both the gas and solid phases. The boundary condition at the top of the bed is a pressure boundary fixed at a reference value (atmospheric).
Solids are free to leave if entrained and then return to the computational domain from the bottom inlet with a same mass flux.
how i can fix this in fluent??? i mean this condition ''Solids are free to leave if entrained and then return to the computational domain from the bottom inlet with a same mass flux.''
thanks