What is it about?
The paper provides insight into the dynamic behaviour of the apparent (macroscopic) contact angle θ and its dependence on contact-line velocity at various degrees of surface wetting. The results reveal that surface wettability has a critical influence on dynamic contact angle behaviour. The work concludes that even for a single liquid, there is no universal expression to relate contact angle with contact-line speed.
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Why is it important?
Many numerical models of liquid interactions with solid surfaces (e.g. droplet impact) require expressions of the dependence of contact angle on contact-line speed. Contact angle behaviour is intimately related to impact spreading dynamics and impact outcome (sticking, rebound, etc.). Thus, the inability to capture the correct contact-line dynamics, may cause model failure in predicting the correct physical outcome.
Perspectives
We studied many cases of water droplets impacting axisymmetrically on substrates with low to moderate Weber numbers, and with wettabilities ranging from low (contact angle above 140 deg) to high (contact angle below 40 deg). The goal was to maximize insight on contact-angle dynamics under unsteady flow conditions.
Constantine Megaridis
University of Illinois at Chicago
Read the Original
This page is a summary of: Contact angle dynamics in droplets impacting on flat surfaces with different wetting characteristics, Journal of Fluid Mechanics, July 2006, Cambridge University Press,
DOI: 10.1017/s0022112006000231.
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