| Three-dimensional interactions between a Rankine vortex advecting in a base-flow and colliding with a droplet have been investigated through a computational solution to the Navier-Stokes, continuity, energy and species equations. Particular attention is given to the vortex-induced fluctuations on the droplet convective heating (Nusselt number) with and without vaporization, and to the droplet vaporization (Sherwood number).;In the absence of vaporization, Nusselt number perturbations vary monotonically with the vortex initial circulation, the base-flow Reynolds number, and exponentially with the initial vortex distance from the droplet. If the droplet is subject to the vortex influence in a stratified temperature field, i.e. to the coupled flow-thermal perturbations, the vortex influence on the Nusselt number variations is augmented appreciably; here the Nusselt number variations depend explicitly on the values of the temperature profile, a feature absent in such mechanisms taking place in a uniform temperature field. The vortex influence is maximum when the droplet initial distance is two length-scales from the base-flow symmetry axis. Though the problem is unsteady by nature, global self-similarity is observed and correlations are established. The correlation is shown to be valid for solid sphere heating in comparable conditions.;Vortex collision with a vaporizing droplet indicates that Stefan flux not only inhibits the droplet heating, it also 'cuts off' the droplet surface developments from the events in the main flow and the vortex motion. Fluctuations in both Nusselt and Sherwood numbers exhibit self-similarity in both the temporal and time-averaged response. Correlations are therefore established, revealing that Sherwood number fluctuations are enhanced with an increase in the vortex circulation and/or the base-flow Reynolds number and show maximum variations when the vortex initial distance is two length-scales from the base-flow symmetry axis. The correlations are shown to be valid for at least three common fuel droplets (n-heptane, n-octane, n-decane).;All of the resulted correlations, which quantify the effect of vortex collision on the droplet heating and vaporization, compliment the existing ones commonly used for droplets in axisymmetric flows. Based on the results of this study, it can be shown that in spray combustion systems, vortical structures could have significant effects on droplets heat transfer and vaporization, modifying their vaporization rate and local mixture ratio. |
