Quantitative description of droplet dispersion of hollow cone spray in gaseous crossflow

In this study, we experimentally investigate the large-scale vortex pair formed by droplets in the spanwise direction of the flow field of a hollow cone spray injected transversely into a gaseous crossflow. Experiments are conducted in a square channel for a wide range of spray and crossflow conditions. The spatial and velocity distributions of the spray droplets for different cross-sections of the flow field in terms of different flow conditions are measured through flow visualization. Three parameters, namely, vortex vorticity, depth of vortex core, and distance between both vortex cores, are used to characterize the counter-rotating vortex pair (CVP) formed by droplets. The crossflow Reynolds number, (initial atomized) droplet Reynolds number, and number of droplets injected per unit time are all found to significantly influence the features of droplets CVP. We newly define the spray-to-crossflow momentum flux ratio (J∗) based on the injected momentum flux of initial atomized droplets. Accordingly, we develop a set of correlations for predicting the features of droplets CVP based on experimental measurements and the Buckingham π theorem. The results show that these correlations well predict all measured conditions. The results of this study should provide insights into the dynamics of spray droplets in a crossflow and an understanding of the large-scale mixing between a hollow cone spray and a crossflow.