Liquid distribution after head-on collision of two immiscible liquid droplets

What is it about?

The outcome of a head-on collision of two immiscible liquid droplets is studied. When they collide, the droplets can either bounce off each other, coalesce, or separate with the formation of smaller droplets. We are especially interested in the separation. Three different distributions of the liquids are possible here: either two encapsulated droplets form (single reflex separation), or a single encapsulated droplet plus a droplet made solely of the encapsulating liquid emerge, the latter being found either on the impact side (reflexive separation) or opposite to it (crossing separation). The aim of the study is to understand and predict the liquid distribution after separation. The analysis of a large amount of experimental and simulation data has been performed to consider various conditions, including partial and total wetting and a wide range of Weber and Reynolds numbers. This has helped us to understand the factors that influence the final liquid distribution. We have derived two dimensionless parameters that predict the mechanism in very good agreement with experimental and numerical results.

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Photo by V Srinivasan on Unsplash

Photo by V Srinivasan on Unsplash

Why is it important?

Collisions of immiscible droplets are not yet as well studied as collisions of droplets of the same liquids, although they are relevant in many engineering and life-science applications. In this study, we focus on head-on collisions of immiscible droplets that have separation as a collision outcome. We explain the underlying mechanisms. The derivation of two dimensionless parameters allows the prediction of the liquid distribution after separation.

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