Measurements of interfacial properties with the axisymmetric bubble-shape analysis technique: effects of vibrations

We studied the effects of perturbation by vibration on the surface tension and surface area data obtained with the bubble-profile fitting method, using a typical laboratory apparatus. Examining an air bubble issuing downwards from a capillary tip, inside a vessel containing water, we report experimental observations about the effect of multifrequency vibrations on the bubble profile, either in the non-resonance or in the resonance condition, for some normal oscillation modes of the bubble and of the liquid body. Experimental results are given with regard to multifrequency-vibration disturbances on determination of the static surface tension of the liquid and the geometrical properties of the bubble, as a function of acceleration amplitude of vibration. Also, illustrative experimental observations are presented of the dynamic surface tension response to a surface area change, for a surfactant solution, under the action of vibration motion. In the frequency-acceleration plane, we show negligible effects on surface data in the 0-100 Hz and 0-5mg domain, for the geometrical configuration examined and the overall experimental system. The tolerability limit appears at 10mg acceleration, where excitation of the bubble resonance oscillation may occur with significant amplitude. The conclusions are also useful for estimation of the vibration effects in different configurations. (C) 1998 Elsevier Science B.V. All rights reserved.