  An interface-resolved simulation of the combustion of a fuel droplet
suspended in normal gravity is presented in this work, followed by an extensive
analysis on the physical aspects involved. The modeling is based on
DropletSMOKE++, a multiphase solver developed for the modeling of droplet
vaporization and combustion in convective conditions. A wide range of phenomena
can be described by the model, including the interface advection, the
phase-change, the combustion chemistry, non-ideal thermodynamics and
multicomponent mixtures. To our knowledge, this is the most detailed simulation
performed on this configuration, providing a useful theoretical and numerical
support for the experimental activity on this field. A recent experimental work
is used as a reference, in which a methanol droplet is suspended on a quartz
fiber and ignited at different oxygen concentrations. The numerical analysis
offers a detailed insight into the physics of the problem and a satisfactory
agreement with the experiments in terms of diameter decay, radial temperature
profiles and sensitivity to the oxygen concentration. The vaporization rate is
affected by the thermal conduction from the fiber, due to the high temperatures
involved. Moreover, the fiber perturbs the flame itself, providing quenching at
its surface. The combustion physics is compared to the one predicted at
zero-gravity, evidencing a lower standoff-ratio, a higher flame temperature and
an intense internal circulation. The distribution of the species around the
droplet shows (i) a local accumulation of intermediate oxidation products at
the fiber surface and (ii) water absorption in the liquid phase, affecting the
vaporization rate.
