Dependence of the Brazil-nut prediction on viscous-suspension and thin-film assumptions

Ascertain how dependent the prediction that larger particles increase in concentration toward the free surface (Brazil-nut effect) is on assuming a viscous suspension with thin-film lubrication and rapid normal-direction equilibration; quantify how relaxing these modeling assumptions affects the predicted segregation.

Background

The model assumes particles are suspended in a viscous fluid and uses thin-film approximations with rapid equilibration in the normal direction to derive equilibrium profiles.

While the model yields the Brazil-nut effect, the authors explicitly state uncertainty about how strongly this conclusion relies on these assumptions.