Early Stages of Drop Coalescence

Despite the large body of research on coalescence, firm agreement between experiment, theory, and computation has not been established for the very first moments following the initial contact of two liquid volumes. Combining a range of experimental and computational modeling approaches in two different geometries, namely drop-drop and drop-bath configurations, we have been able to elucidate the influence of the intervening gas and van der Waals forces on coalescence. For simple liquids considered here, the gas influences both pre- and post-contact regimes, with jump-to-contact being the primary mode of merging. Subsequently, wave-like air pockets are observed and ultimately influence the initial opening dynamics of the neck.