Wilson, M. C. T., Summers, J. L., Shikhmurzaev, Y. D., Clarke, A. and Blake, T. D. (2006) Nonlocal hydrodynamic influence on the dynamic contact angle: Slip models versus experiment. Physical Review E, 73 (4). 041606. ISSN 1539-3755Full text available as:
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Experiments reported by Blake et al. [Phys. Fluids. 11, 1995 (1999)] suggest that the dynamic contact angle formed between the free surface of a liquid and a moving solid boundary at a fixed contact-line speed depends on the flow field/geometry near the moving contact line. The present paper examines quantitatively whether or not it is possible to attribute this effect to bending of the free surface due to hydrodynamic stresses acting upon it and hence interpret the results in terms of the so-called ``apparent'' contact angle. It is shown that this is not the case. Numerical analysis of the problem demonstrates that, at the spatial resolution reported in the experiments, the variations of the ``apparent'' contact angle (defined in two different ways) caused by variations in the flow field, at a fixed contact-line speed, are too small to account for the observed effect. The results clearly indicate that the actual (macroscopic) dynamic contact angle, i.e.\ the one used in fluid mechanics as a boundary condition for the equation determining the free surface shape, must be regarded as dependent not only on the contact-line speed but also on the flow field/geometry in the vicinity of the moving contact line.
|Copyright, Publisher and Additional Information:||© 2006 American Physical Society. This is an author produced version of a paper published in Physical Review E . Uploaded in accordance with the publisher's self-archiving policy.|
|Keywords:||wetting, slip, moving contact-line, contact angle, surface tension, liquid film, coating|
|Academic Units:||The University of Leeds > Faculty of Engineering (Leeds) > School of Mechanical Engineering (Leeds) > Institute of Engineering Thermofluids, Surfaces & Interfaces (iETSI) (Leeds)|
|Depositing User:||Dr Mark Wilson|
|Date Deposited:||28 Feb 2008 11:25|
|Last Modified:||08 Feb 2013 17:05|
|Publisher:||American Physical Society|
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