The transport of a wettable sphere through a fluid-fluid interface : high Bond numbers (AGGREGATION CH 11)

Abstract

In the previous chapter, we studied the transport of wettable spheres through the interface of a demixed colloid-polymer mixture at low Reynolds and Bond numbers by confocal microscopy. Here we consider the high Bond number - low Reynolds number scenario. The sphere approaches the interface from the polymer-rich phase and is eventually transported to the colloid-rich phase. In the high Bond number limit, wetting forces do not play a large role in the transport, even though the spheres are wettable by the colloid-rich phase. Depending on the Bond number, we find two scenarios. At moderately high Bond numbers, the sphere leaves a V-shaped interface behind, which recovers due to interfacial flow. At higher Bond numbers, the so-called tailing regime is observed. In this regime, the spheres leave long columns of gas behind, which break up through a Rayleigh-Plateau instability. Furthermore we find that the theoretical expression for the approach of a sphere toward an undeformable free interface holds surprisingly well for strongly deforming interfaces.