Film deposition in non-wetting tubes: An experimental film thickness law

Copyright © 2015 by ASME. Deposition of a liquid film on non-wetting tubular surfaces gives rise to the unexpected behavior of simultaneously coexisting thick and thin films. Experiments show that a discontinuity in the film thickness, a jump between the thick and thin films being laid from the meniscus towards the bounding moving contact line, occurs after a considerably thicker than the expected Bretherton film is deposited. Bretherton assumed the film to be uniform and, unlike the case of a non-wetting surface, the viscocapillary deposition process was not affected by the presence of a contact line. In reality this phenomenon lies at the confluence between a dewetting process and the deposition itself, being the result of the influence claimed by the dynamics of the zone adjacent to the moving contact line. The film thickness is calculated directly from the experimental data and a correlation is obtained by matching the measured and the theoretical shock velocities associated with the hydraulic jump. The non-wetting film is significantly thicker than Bretherton\u27s prediction and follows in turn a different law which is determined experimentally. The nonwetting film thickness is found to vary as h4=3 R , hR being the Cadependent non-dimensional Bretherton film thickness