High-Speed Impact of Water Droplet upon Wet Surface with Different Surface Tension
Date Issued
2008
Date
2008
Author(s)
Cheng, Kai-Ren
Abstract
The main objective of this study is experimental investigation of the droplet-film collision under the conditions of different surface tension and different Weber number. In the experiment, we control the size and the colliding velocity of droplet. To change the surface tension of water, the surfactant was used. In present experimental study, the special attention is given to the generation of high-speed droplets, including which is the best cut-off length of liquid jet in order to form droplets. Secondly, the phenomena of impingement after droplet impacts the liquid film with different surface tension is also in the focus of this investigation. The experimental results of droplet-film impact are presented in this thesis. The dependencies of splashing threshold on different surface tension are obtained. It was found that both the length and the cross-sectional radius of liquid jet significantly affect the forming time of droplets during the cut-off process under high speed conditions. They cause the decrease in the droplet velocity and therefore, the decrease in the Weber number. Base on it, one can conclude that the optimal cut-off length is consequently important. Depend on the changes of Weber number and non-dimensional thickness (H), the five characteristic regimes may be singled out: (I) Merging, (II) C-J, which implies center-jet, (III) C-J and 2nd droplet, (IV) Multiple droplets, and (V) Closed. The influence of surface tension on impinging phenomena is discussed in this thesis.
Subjects
droplet collision
high-speed droplet
surface tension
Weber number
surfactant
Type
thesis
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