How Water Droplets in Electric Field Avoid Merging: A Numerical Study of Their Interactions

What is it about?

Under favorable conditions, the separation of emulsions consisting of two immiscible liquids can be achieved using a strong electric field. If the impurity droplets are conductive, they approach each other in the external field and merge, becoming large enough to either float to the surface or settle to the bottom on their own. However, if the strength of the external field is too high, the droplets, upon contact, may fail to merge and instead bounce off each other or even break apart into many smaller fragments, worsening the situation. In our study, we investigated how the outcome of such "unsuccessful" interactions depends on the size of the droplets and the strength of the external field. Numerical modeling was employed for this purpose, allowing us to study in detail how the forces acting on the droplets are distributed and why they lead to specific disintegration scenarios. Computer simulations enable an unlimited number of virtual experiments, and as a result, we developed a comprehensive "Regime Map" of droplet interactions. This "Regime Map" is a diagram that clearly illustrates which outcome will occur for any given combination of droplet size and electric field strength.

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Photo by Pete Godfrey on Unsplash

Photo by Pete Godfrey on Unsplash

Why is it important?

Previously, the negative outcomes of droplet interactions were rarely considered, despite their frequent occurrence in technical processes. Additionally, the paper provides a detailed description of the numerical simulation approach, which can be useful for solving various problems in two-phase hydrodynamics, particularly in electrohydrodynamics.

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