The effects of thin films on the hydrodynamics near moving contact lines

Abstract

We explore the effects of thin films on the hydrodynamics of macroscopic fluid bodies spreading over solid surfaces. To examine these effects, we measure the interface shape within microns of moving contact lines and compare those measurements to two asymptotic models in the limit of small capillary number, Ca. One model requires that the films affect the hydrodynamics only in a microscopic region near the contact line and allows the macroscopic meniscus to exhibit a nonzero effective contact angle. The other model describes the film as containing mobile fluid and specifically models the flow as fluid moves into or out of the film as the contact line moves. We examine fluids advancing and receding on wetting and nonwetting surfaces with spontaneously forming (molecular scale) and pre-existing (micron scale) films. Our results emphasize the importance of the mobility of the molecules in these very thin films in determining the hydrodynamics governing the moving contact line. The first model, which describes fluids advancing over dry surfaces, also accounts for the hydrodynamics of liquids advancing over very thin, immobile films. Surprisingly, the same model fails when fluid recedes on a nonwetting surface and no film is present. For mobile pre-existing films, the second model, based on Landau and Levich’s theory, accounts for the hydrodynamics in the limit of small Ca.

Parameters affecting maximum fluid transport in large aperture fractures

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Thin-Film Flows And High-Order Degenerate Parabolic Equations

“…This 'lifting' regularisation is widely used in the analysis literature and is the one with the most straightforward physical interpretation; it is thus also popular in both theoretical and experimental studies of droplet spreading -see, for example, Voinov (1977), Tanner (1979), Kalinin and Starov (1986), Stoev et al (1998), Chebbi (1999) and Diez et al (2001). An asymptotic analysis of the limit c -t 0+ (King and Bowen (2001» to leading order, so in the case of (12) we have…”

A mathematical model for atmospheric ice accretion and water flow on a cold surface

“…In particular, the mass balance (15), in the absence of ice formation, is typical of free surface thin film flows. These are notoriously difficult to solve in the vicinity of a moving contact line [38,39,18,40]. For this reason the numerical work of the following sections deals initially with the water flow; the complication of freezing is a relatively simple extension.…”