Proceedings

EPJ ST Highlight – Observing Flows at a Liquid-Liquid-Solid Intersection

Cameras and lasers measure the flow fields near a liquid-liquid moving contact line. Gupta et al. 2024

Experiments reveal how a liquid-liquid interface interacts with a moving contact line.

Most of us are familiar with the classic example of a liquid-gas moving contact line on a solid surface: a raindrop, sheared by the wind, creeps along a glass windscreen. The contact line’s movements depend on the interplay between viscous and surface tension forces - a relationship that has been thoroughly investigated in experimental fluid mechanics. In a study published in EPJ Special Topics (EPJ ST), Harish Dixit, of the Indian Institute of Technology Hyderabad, and his colleagues now examine the movements of a contact line formed at the interface between two immiscible liquids and a solid. The experiments fill a gap in fluid dynamics and suggest a mechanism for an imposed boundary condition that eludes mathematical description.

According to theory valid in the viscous limit, the movement of a liquid-liquid contact line should be governed entirely by the liquids’ viscosity ratio and the angle at which the liquid interface meets the solid. To examine this in a real-world system, Dixit and his colleagues filled a rectangular tank with two liquid layers—silicone oil atop sugar water - with similar densities but significantly different viscosities. The researchers placed a glass slide at the edge of the tank, which they could slide vertically to create a moving contact line.

Using a technique that tracks tiny particles introduced to the liquids and illuminated with laser light, the researchers simultaneously mapped the flow field on both sides of the liquid-liquid interface while they moved the glass slide. They found that the flow velocities rapidly decreased close to the contact line. Additionally, the liquid interface appeared to slip along the moving glass slide, rather than staying pinned to it - resolving the apparent “singularity” in models that impose a no-slip boundary condition on the moving wall.

The findings lend support to theoretical models of contact line dynamics, and offer parameters that could improve numerical simulations which are based on similar-viscosity liquids.

This was our first experience of publishing with EPJ Web of Conferences. We contacted the publisher in the middle of September, just one month prior to the Conference, but everything went through smoothly. We have had published MNPS Proceedings with different publishers in the past, and would like to tell that the EPJ Web of Conferences team was probably the best, very quick, helpful and interactive. Typically, we were getting responses from EPJ Web of Conferences team within less than an hour and have had help at every production stage.
We are very thankful to Solange Guenot, Web of Conferences Publishing Editor, and Isabelle Houlbert, Web of Conferences Production Editor, for their support. These ladies are top-level professionals, who made a great contribution to the success of this issue. We are fully satisfied with the publication of the Conference Proceedings and are looking forward to further cooperation. The publication was very fast, easy and of high quality. My colleagues and I strongly recommend EPJ Web of Conferences to anyone, who is interested in quick high-quality publication of conference proceedings.

On behalf of the Organizing and Program Committees and Editorial Team of MNPS-2019, Dr. Alexey B. Nadykto, Moscow State Technological University “STANKIN”, Moscow, Russia. EPJ Web of Conferences vol. 224 (2019)

ISSN: 2100-014X (Electronic Edition)

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