Experiments On Surface Waves In Thin Wetting Films

A new method for excitation and measurement of time stationary, free running waves on wetting films is described. The waves in the frequency range of 10-140 Hz are generated by an oscillating bubble against a quartz plate in a Derjaguin-Scheludko film balance. The results from the experimentally measured dispersion equation are compared with a theoretical model based on the lubrication approximation. It is shown that there are significant discrepancies between experiment and theory which cannot be explained by the classical DLVO-theory as well as by the assumption of a non-slip boundary condition. (C) 1999 Elsevier Science B.V. All rights reserved.