(As an exercise, substitute in the expression for terminal velocity with , and use the criterion to obtain the above expression, for the Stoke’s regime)
Hindered settling
If there are particles in the fluid, then the settling of a single particle will be influenced by the presence of the neighboring particles. In such case, the settling velocity is larger than that of a single–particle.
where is the volume–fractions (not bed–porosity) of fine–suspension of particles in fluid,
The viscosity of a suspension is also affected by the presence of the dispensed phase and should be accordingly used in the calculation of Reynolds number:
= viscosity of suspension;
= viscosity of pure fluid
in the expression for terminal velocity with 
, and use the criterion 
to obtain the above expression, 
for the Stoke’s regime)
is the volume–fractions (not bed–porosity) of fine–suspension of particles in fluid,
= viscosity of suspension;
= viscosity of pure fluid 
