Abstract
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.
Highlights
In recent years, the growth of computational power is being exploited in scientific computing, and exascale simulations are on track to be the major breakthrough in the field
The background carrier phase is coloured by the vapour mass fraction, the droplets are coloured by their temperature
Given the strong coupling between the physical phenomena involved in our case, it will be shown that this division is relevant for the description of the droplet migration and turbulence modulation as well
Summary
The growth of computational power is being exploited in scientific computing, and exascale simulations are on track to be the major breakthrough in the field. We venture for the first time into DNS of spray evaporation in turbulent flow with four-way coupling of the carrier and dispersed phases, and interface resolved phase change at the droplet level, under conditions that approach those encountered in spray combustion applications, using the method proposed by Lupo et al [12]. This allows for the direct solution of 14081 “cold” droplets evaporating in a “hot” turbulent channel flow, by a combination of physical assumptions (droplet sphericity) and numerical techniques (immersed boundary treatment of the gas-liquid interface).
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