Viscous resuspension of droplets

Abstract

Using absorbance measurements through a Couette cell containing an emulsion of buoyant droplets, volume fraction profiles are measured at various shear rates. These viscous resuspension experiments allow a direct determination of the normal stress in connection with the suspension balance model that has been developed for suspensions of solid particles. The results unambigously show that the normal viscosity responsible for the shear-induced migration of the droplets is the same as for rigid particles, even at moderate capillary numbers where coalescence occurs, and independently of the polydispersity. This implies that neither the particle deformation nor the detail of contact interactions play an important role on shear-induced migration.