Self-excitation of Leidenfrost drops and consequences on their stability.
basic_science · Level V
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- Record sourced from PubMed, PMID 34155101.
- Also identified by DOI 10.1073/pnas.2021691118 and PMC identifier 8256046.
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Abstract
Volatile liquids (water, alcohol, etc.) poured on hot solids levitate above a layer of vapor. Unexpectedly, these so-called Leidenfrost drops often suddenly start to oscillate with star shapes, a phenomenon first reported about 140 y ago. Similar shapes are known to be triggered when a liquid is subjected to an external periodic forcing, but the unforced Leidenfrost case remains unsolved. We show that the levitating drops are excited by an intrinsic periodic forcing arising from a vibration of the vapor cushion. We discuss the frequency of the vibrations and how they can excite surface standing waves possibly amplified under geometric conditions of resonance-an ensemble of observations that provide a plausible scenario for the origin, mode selection, and sporadic nature of the Leidenfrost stars.