| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 96 === The investigation on the droplet impact behavior has been proceeded for more than
several decades. Several different factors affecting the spreading behavior of the impinging
droplet have been reported, such as the initial impact velocity, droplet size, liquid viscosity,
and the surface property of solid.
Two major issues were studied in this work: surface effect and surfactant effect. In
the first part, water droplet impinges five different solid surfaces at a fix initial impact
velocity. The spreading behaviors were then investigated for these five solid surfaces with
different hydrophobicity. The equilibrium contacts of these five surfaces were
paraffin>Teflon>rough glass>quartz>clean glass. In the second part of this work, aqueous
droplets consisting of different surfactants with surface tension impinge the clean glass
surface. The spreading behaviors were then studied to check the effect of tension and
surfactant.
The experiments were performed by using a high speed CCD. 2905 images per
second were captured sequentially. The drop profiles were then obtained from the drop
images. Information D0 (initial diameter), u0 (impact velocity), t0 (impact image), θ
(contact angle), d (spreading diameter), H (apex height) were further resulted from the
drop profiles. The relationship between the dimensionless groups (spreading factor, d/D0;
apex factor, H/D0; time, tu0/D0) was investigated. The images captured from 45 degree top
view were also compared with the silhouette to detail the concavity of impinging droplet.
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