Oil droplet wetting dynamics on immiscible liquid surfaces

The wetting dynamics of an immiscible oil with water has been long studied owing to its ubiquitous nature and applicability in disparate scenarios such as oil spills, agriculture and cosmetics. Although plenty of literature exists on spreading of spreading oils on water, or droplet impacts on alike substrates, comparatively little is known about the spreading dynamics of an oil that is inherently non-spreading on water. In the present work we analyze the scenario which involves the interaction of an oil droplet with a bulk liquid using high speed visualization. The topological transitions observed are systematically characterized in terms of the governing non-dimensional parameters and associated dominant force balances are established. A physical explanation and criteria for the occurrence of various transitions with appropriate scaling arguments is provided. Our results aim to further current understanding on interactions in oil/water systems and elucidate the underpinning physical mechanisms.