Authors Karakashev, S. I. ; Stöckelhuber, K.W. ; Tsekov, R. ; Heinrich, G. ; Phan, C. M.
Title Tribology of thin wetting films between bubble and moving solid surface
Date 01.08.2014
Number 40362
Abstract This work shows a successful example of coupling of theory and experiment to study the tribology of bubble rubbing on solid surface. Such kind of investigation is reported for first time in the literature. A theory about wetting film intercalated between bubble and moving solid surface was developed, thus deriving the non-linear evolution differential equation with account for the friction slip coefficient at the solid surface. The stationary 3D film thickness profile, which appears to be solution of the differential equation, for each particular speed of motion of the solid surface was derived by means of special procedure and unique interferometric experimental setup. This allowed us to determine 3D map of the lift pressure within the wetting film, the friction force per unit area and the friction coefficient of rubbing at different speeds of motion of the solid surface. Thus, we observed interesting tribological details about the rubbing of the bubble on the solid surface like for example:<br />1. A regime of mixed friction between dry and lubricated frictions exists in the range of 6 – 170 µm/s, beyond which the rubbing between the bubble and solid becomes completely lubricated and passes through maximum;<br />2. The friction coefficient of rubbing has high values at very small speeds of solid’s motion and reduces substantially with the increase of the speed of the solid motion until reaching small values, which change insignificantly with the further increase of the speed of the solid.<br />Despite the numerous studies on the motion of bubble/droplet in close proximity to solid wall in the literature, the present investigation appears to be a step ahead in this area as far as we were able to derive 3D maps of the bubble close to the solid surface, which makes the investigation more profound.
Publisher Advances in Colloid and Interfaces Science
Citation Advances in Colloid and Interfaces Science 210 (2014) 39-46
Tags thin wetting films tribology stribeck curves friction lift force

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