Numerical simulation of impinging spray characteristics under high ambient pressures with an improved droplet collision model

Abstract

Impinging spray characteristics under high ambient pressures (10–60 atm) were investigated experimentally and numerically. A recently proposed pressure-dependent droplet collision model was adopted to determine the collision outcomes. The results being compared to the predictions of Estrade et al. and O’Rourke’s droplet collision models. The comparison shows that the present pressure-dependent model accounts for the previous experimental observation and theory that increasing of ambient pressure promotes droplet bouncing, which was absent in the predictions of Estrade et al. and O’Rourke’s droplet collision model. Moreover, Estrade et al. and O’Rourke’s model tend to over-predict droplet size under high ambient pressures, results in the multi-tips in the spray shape, which however was seldom seen in the experimental shadowgraphs and predictions of the present model. Additionally, predictions of present model also account for the previous experiment that increasing of ambient pressure suppresses droplet breakup. Droplet velocity characteristics of impinging sprays under different ambient pressures were further investigated. The results show that, increasing of ambient pressure plays more aerodynamic resistance on the droplet together with the droplet bouncing-induced kinetic energy dissipation result in the reduced droplet velocity, and long-time droplet velocities tend to “converge”.