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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? Scientists have now explained why under certain conditions, a droplet of liquid should not coalesce with the liquid surface below. 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.
This temperature difference generates a recirculating flow that is visualized by shining a green laser light on fluorescent particles that are added as passive tracers within the drop. The researchers' results can be used to characterize the spread of certain chemical and biological agents that are transferred through raindrops and sprays.Image credit: MIT
