Direct numerical simulation of spray droplet evaporation in hot turbulent channel flow

We perform a direct numerical simulation (DNS) of 14081 cold spherical droplets evaporating in a hot fully-developed turbulent channel flow. This effort is the first extensive computation that employs four-way coupling of the droplet motion with the turbulent carrier phase and interface-resolved evaporation dynamics, for a flow configuration that approaches conditions encountered in spray combustion applications. The complex interaction of momentum, heat, species transfer and phase change thermodynamics is explored. Large-scale droplet motion, modulation of the carrier phase turbulence, and influence of the mean and turbulent mass transport on the evaporation dynamics are observed and quantified. Based on the data set, phenomenological explanations of the shear-induced migration of the dispersed phase and of the effect of turbulent mass transport on the evaporation are provided. The transient nature of the DNS is exploited to generate a novel database that samples a range of turbulence and evaporation timescales, from which a model for the enhancement of the evaporation rate by the ambient turbulence is extracted.