Combustion of droplets in turbulence

The combustion of droplets in turbulence involves complex, interacting phenomena. First, the droplets cluster in regions of low vorticity and modulate the velocity fluctuations of the gas. Second, the droplets release vapor and energy, which then mix with the gas. Third, the vapor reacts with the oxidizer creating diffusion flames, which surround individual droplets or droplet clusters, and premixed flames, which propagate through mixtures of vapor and oxidizer.\footnote{Jenny, Roekaerts, and Beishuizen, \emph{Progress in Energy and Combustion Science} \textbf{38}, 846-887 (2012).} \par These phenomena are investigated with direct numerical simulations. The gas phase is modeled with the low Mach number approximation, and the droplets are modeled as point droplets.\footnote{Weiss, Giddey, Meyer, and Jenny, \emph{Physics of Fluids} \textbf{32}, 073305 (2020).} The combustion of vapor and oxidizer is modeled with a one-step reaction mechanism. Droplet clusters are analyzed with Vorono\"{i} tessellations, and diffusion and premixed flames are identified with Takeno's flame index.\footnote{Yamashita, Shimada, and Takeno, \emph{26th Symposium on Combustion}, 27-34 (1996).} Simulations with different droplet diameters, droplet number densities and turbulence intensities are performed.