Slip velocity during the flow of a liquid over a solid surface

• Published in: The European physical journal. ST, Special topics Special topics, 2011-08, Vol.197 (1), p.203-209
• Main Author: Ruckenstein, E.
• Format: Article
• Language: English
• Subjects: Atomic; Classical and Continuum Physics; Condensed Matter Physics; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Materials Science; Measurement Science and Instrumentation; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Regular Article; Solid surfaces and solid-solid interfaces; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Wetting
• ISSN: 1951-6355; 1951-6401
• DOI: 10.1140/epjst/e2011-01460-9

An equation is derived for the slip velocity when a nonequilibrated drop is spreading over a solid surface. This velocity is obtained as the product of the force induced by the gradient of the chemical potential along the surface with Einstein’s expression for the mobility of the molecules. A similar approach was applied to the flow in a capillary. In that case, the surface diffusion coefficient evaluated by comparing the obtained theoretical expression with experiment is orders of magnitude larger than expected. For this reason, one concludes that the observed slip is apparent and is caused by the formation of a gap of gas separating the flowing liquid from the solid surface.