Experimental observation of a confined bubble moving in shear-thinning fluids

When a confined bubble translates in a cylindrical capillary tube, a thin film of liquid separates the bubble surface and the tube inner wall, with its thickness determined by the interplay of viscous, inertial and capillary effects. Although the dynamics of a bubble in a Newtonian liquid has been the subject of several studies since the pioneering works of Taylor and Bretherton, the case where the fluid exhibits a non-Newtonian behavior is not much understood. In applcations such as enhanced oil recovery and drug delivery, the fluids are likely to exhibit non-Newtonian properties. In this work, we consider the classical Bretherton problem with non-Newtonian fluids. We provide quantitative measurement of the thickness of deposited liquid film for carboxymethyl cellulose (CMC) and Carbopols solutions with different concentrations in a wide range of Capillary numbers. We further compare our investigations with the scaling law considering the effecitve viscosity to extend the classical Bretherton's correlations non-Newtonian fluids. Our results may enrich the fundamental understanding of the multi-phase flows involving non-Newtonian fluids.