Capillary flow of two immiscible liquids initially separated by a Taylor gas bubble

We investigate the capillary displacement of silicone oil columns by water in tandem with a Taylor gas bubble in horizontally aligned tubes that initially separate the two immiscible liquids. The experiments show that the gas slug's motion forces the drainage of the prefilling liquid through a thin film deposited on the tube's wall. The displaced oil is then recovered at the advancing water meniscus. The dynamics of the capillary displacement and drainage are studied as functions of the silicone oil and gas bubble volumes. We find that the Taylor bubble's length has a small influence on the capillary displacement and drainage of the prefilling liquid. The study presents an adapted model for the capillary drainage and oil recovery using Taylor's law for the deposited film thickness on the tube's wall, which collapses all experimental data onto a single curve.