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Free keywords:
complex fluids, condensation/evaporation, drops
Abstract:
Tracer particles are the workhorse of the fluid dynamicist for visualizing flow in
transparent liquids. Thus a tracer becomes useless if its signal disappears, which
frequently happens in practice, for instance due to bleaching. The opposite occurs
in a recent work by Kim & Stone (J. Fluid Mech., vol. 850, 2018, pp. 769–783):
the fading signal of a dissolving particle may reveal the local composition in a
mixture. Such information is highly valuable in the study of evaporating droplets.
In virtually all realistic cases, droplets consist of multiple components, ranging from
trace impurities to engineered cocktails, which, for instance, generate a desired deposit
pattern for a printing process. Different components typically evaporate at different
rates, which causes inhomogeneities in droplet composition. Determining the latter is
one of the main challenges in the field.
