The ratio of widths R between two phases of a stationary stratified flow for which the phase interface is parallel to the side walls of a rectangular slit is calculated under the condition that the two phases give equal volume fluxes. For a combination of two Newtonian fluids, the width ratio Ris simply proportional to their viscosity ratio. If both components are of the power-law type, R is greater than the viscosity ratio and increases with the amount of shear-thinning (pseudo plasticity) of the higher viscosity component. For a combination of a Bingham fluid with a Newtonian fluid R decreases with increasing yield stress of the former.Measurements of R were made on various combinations of polyvinyl alcohol (PVA) solutions and of suspensions of CaCO3 in PVA solutions. In the former cases, the experimental values were in good agreement with the theoretical values for the power-law fluids. In the latter, R was primarily affected by the yield stress as predicted by the theory, but a correction was found to be necessary for the shear-thinning effect.
展开▼
