Confined flow behaviour of droplets in microcapillary flow.

The problem of droplets flowing in a micritions is relevant in several applications including flow in porous media. When the flow in the capillary is laminar with negligible gravity effects, droplet velocity and deformation depend upon three independent parameters: the droplet size relative to the capillary radius [Formula: see text][Formula: see text], which is a measure of confinement, the viscosity ratio [Formula: see text] between the droplet and the continuous phase and the capillary number Ca which measures the ratio of viscous to capillary forces. Although droplet microconfined flow behaviour in capillaries has been widely investigated by theoretical models, experimental results are still scarce. Here, an experimental campaign focused on the flow behaviour of axisymmetric confined droplets flowing in a microcapillary is carried out. Our experimental results were obtained by using a water in soybean oil emulsion with a low viscosity ratio and the effect of the aforementioned three parameters, [Formula: see text], [Formula: see text] and Ca, on droplet motion was investigated. Moreover, our experimental results are compared with numerical solutions available in the literature.