Direct numerical simulation of inert droplet effects on scaler dissipation rate in turbulant and non-reacting shear layers

Jun, Xin and Luo, Kai H. (2009) Direct numerical simulation of inert droplet effects on scaler dissipation rate in turbulant and non-reacting shear layers. Flow Turbulence and Combustion, 84 (3), 397-422. (doi:10.1007/s10494-009-9238-7).

Abstract

Three-dimensional direct numerical simulation has been performed to investigate the effects of inert evaporating droplets on scalar dissipation rate ? in temporally-developing turbulent reacting and non-reacting mixing layers with the Reynolds number based on the vorticity thickness up to 8000 and the number of traced Lagrangian droplets up to 107. The detailed instantaneous field analysis and ensemble-averaged statistics reveal complex interactions among combustion, droplet dynamics and evaporation, all of which have a considerable influence on ?. The presence of inert evaporating droplets promotes ? in both non-reacting and reacting mixing layers. In the latter, combustion reduces ?, so when combustion is suppressed by evaporating droplets, ? is enhanced. The transport equation of ? has been analyzed to investigate the various effects on ? in detail. The terms in the equation contain explicitly the evaporation rate and its spatial derivative, acting as a sink and a source for ?, respectively. On the whole, the net effect of the evaporation-rate terms is to promote ?. However, the production and dissipation terms are the dominant source and sink terms, respectively.

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