Interaction of droplet dispersion and evaporation in a polydispersed spray

作者：Srikrishna Sahu, Yannis Hardalupas, A. M. K. P. Taylor · 发表于：Journal of Fluid Mechanics · 年份：2018 · DOI：10.1017/jfm.2018.247 · 被引用次数：43 · 研究领域：Particle Dynamics in Fluid Flows、Combustion and flame dynamics、Fluid Dynamics and Heat Transfer

The interaction between droplet dispersion and evaporation in an acetone spray evaporating under ambient conditions is experimentally studied with an aim to understand the physics behind the spatial correlation between the local vapour mass fraction and droplets. The influence of gas-phase turbulence and droplet–gas slip velocity of such correlations is examined, while the focus is on the consequence of droplet clustering on collective evaporation of droplet clouds. Simultaneous and planar measurements of droplet size, velocity and number density, and vapour mass fraction around the droplets, were obtained by combining the interferometric laser imaging for droplet sizing and planar laser induced fluorescence techniques (Sahu et al. , Exp. Fluids , vol. 55, 1673, 2014 b , pp. 1–21). Comparison with droplet measurements in a non-evaporating water spray under the same flow conditions showed that droplet evaporation leads to higher fluctuations of droplet number density and velocity relative to the respective mean values. While the mean droplet–gas slip velocity was found to be negligibly small, the vaporization Damköhler number ( $Da_{v}$ ) was approximately ‘one’, which means the droplet evaporation time and the characteristic time scale of large eddies are of the same order. Thus, the influence of the convective effect on droplet evaporation is not expected to be significant in comparison to the instantaneous fluctuations of slip velocity, which refers to the direct effect of ...