Liquid-Phase Circulation and Mixing in Multicomponent Droplets Vaporizing in aLaminar Convective Environment

摘要

A combined theoretical/experimental study of internal circulation induced bysurface rotation of mm-sized pendant droplets was completed. The study consistently revealed predictable helical three-dimensional circulation patterns that bear little resemblance to the two-dimensional toroidal internal flows established within droplets under axisymmetric convective conditions. The observed complex flow patterns suggested substantially enhanced liquid mixing rates, thus indicating that droplet spinning may be very important in practical situations involving droplet convective transport. In a parallel study, charged droplets up to 100 micrometers in diameter were stably levitated and exposed to uniform air streams with Reynolds numbers up to 3. The evaporation rate of levitated dodecanol droplets was measured under quiescent conditions and followed the familiar d to the power of 2 -law. No detailed information could be obtained on internal circulation of levitated droplets impregnated with scattering or fluorescent agents. Droplet evaporation, Droplet internal mixing, Droplet rotation, Flow visualization, Internal circulation, Multicomponent droplets.