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Flow Transition within an Evaporating Binary Mixture Sessile Drop

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http://prl.aps.org/abstract/PRL/v106/i20/e205701
Original languageEnglish
Article number205701
Number of pages4
JournalPhysical Review Letters
Volume106
Issue number20
Early online date17 May 2011
DOIs
Publication statusPublished - 20 May 2011

Abstract

The flow field along the base of an evaporating ethanol-water droplet and its evolution time was measured by particle image velocimetry. Three stages are revealed, a first stage dominated by multiple vortices, a second transition stage characterized by a remarkable spike in outward flow not previously identified, and a third stage dominated by outward flow identical to that found for pure water. Stage I is thought to be driven by surface tension gradients arising from local concentration variation. The spike in outward flow is explained in terms of a transition corresponding to almost total depletion of ethanol. An exponential decay in vorticity during the transition stage is explained in terms of ethanol diffusion from the bulk to the interface. We speculate on the existence of a zero-concentration wave propagating from the apex to the contact line corresponding to the final total depletion of ethanol.

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