Knowledge of droplet dynamics provides the basis of predicting pressure drops, holdups and corrosion inhibitor distribution in multiphase fl ow. Droplet size and its distribution also determine the separation efficiency between different phases. Experimental observations were conducted for droplet impingements with different fluids, droplet sizes and velocities, and film thicknesses. The observed transition boundaries were compared with the models developed by different authors. For impingement on a deep pool surface, the Marengo and Tropea correlation for splashing does not agree with the experimental results in this study. The Bai and Gosman critical Weber number for bouncing agrees with the water results but not the oil results. Three new correlations for transition boundaries between bouncing, coalescence, jetting and splashing were proposed and compared with the experimental observations. Key words: Droplet, liquid fi lm, transition boundary, high-speed video are different from each other. In the coalescence regime, the droplet submerges in the fi lm accompanied with vortex rings. In the splashing regime, a crown is formed at the early stage of splashing. A number of daughter droplets are formed from the tip of the crown. The crown collapses and recoils toward the crown center at the late stage of splashing. This recoiling will eventually form a liquid jet at the center and generate a secondary droplet from the top of the jet. Normally, bouncing and coalescence only occur under fairly low Weber numbers. Rein (1996) further analyzed the possible sub-regimes during the transition from coalescence to splashing using the Weber number as a criterion.For complicated phenomena, the study of the regime boundaries remains the first priority for a lot of work in the literature. Knowledge of the transition criteria between regimes is critical for the analysis of droplet impact. Several correlations were proposed for prediction of these transitions. Bai and Gosman (1995) collected a number of results from the literature, trying to find a coherent category of the impact phenomena and their thresholds in terms of the dimensionless numbers. For wetted walls with surface temperature lower than boiling temperature, they proposed simple criteria for transitions between bouncing, coalescence and splashing. Cossali et al (1997) investigated the transition from coalescence to splashing by analyzing a large number of pictures. Their correlation was based on the Weber and Ohnesorge numbers, and the liquid fi lm thickness was normalized with the droplet diameter. From detailed experimental studies performed with visualization techniques, Mundo et al (1997;1998) found a correlation that describes the splashing-deposition (coalescence) limit of an individual droplet impacting on a surface with a defined surface
The droplet impacting on dry and wet surface is studied. Splashing was not observed with the impacting velocity up to 600 cm/s for vertical impingement on dry solid surfaces. Transition to splashing happens when the steel surface is wetted and the dry surface is inclined. There is a relationship between the impacting angle and impacting velocity for the transition boundary. The transition impacting angle increases with the increase of the impacting velocity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.