A floating droplet
How can droplets “levitate” on liquid surfaces?

A drop or two of cold cream in hot coffee can go a long way toward improving one’s morning. But what if the two liquids didn’t mix?
MIT scientists have now explained why under certain conditions a droplet of liquid should not coalesce with the liquid surface below – using silicone oil sitting on a warm bath. If the droplet is very cold, and the bath sufficiently hot, then the droplet should “levitate” on the bath’s surface, as a result of the flows induced by the temperature difference.
The team’s results, published in the Journal of Fluid Mechanics, offer a detailed, mathematical understanding of drop coalescence, which can be observed in everday phenomena, from milk poured in coffee to raindrops skittering across puddles, and sprays created in surf zones.
- https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/thermal-delay-of-drop-coalescence/CB55985D6ADC2251BA5EA94C8021C18F
- https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/thermal-delay-of-drop-coalescence/CB55985D6ADC2251BA5EA94C8021C18F