Modification of Shape Oscillations of an Attached Bubble by Surfactants

0393230 - ÚCHP 2014 RIV FR eng J - Journal Article
Vobecká, Lucie - Vejražka, Jiří - Tihon, Jaroslav
Modification of Shape Oscillations of an Attached Bubble by Surfactants.
EPJ Web of Conferences. - (Wang, A.). Roč. 45, č. 2013 (2013), 01095. ISSN 2100-014X.
[Experimental Fluid Mechanics 2012. Hradec Králové, 21.11.2012-23.11.2012]
Institutional support: RVO:67985858
Keywords : bubble oscillations * surfactants * eigenmodes
Subject RIV: CI - Industrial Chemistry, Chemical Engineering

In the experiments, shape oscillations of a bubble are invoked by a motion of a capillary, to which the bubble is injected. Decaying oscillations are recorded and their frequency and damping are evaluated. By changing the excitation frequency, three lowest oscillation modes are studied. Experiments were repeated in aqueous solution of several surfactants at various concentrations. Generally, these features are observed: Initially a surfactant addition leads to an increase of the oscillation frequency; this effect can be attributed to the increasing interfacial elasticity. The decay time of oscillation is strongly decreasing, as a consequence of energy dissipation linked with Marangoni stresses. At a certain critical concentration, frequency decreases abruptly and the decay time passes by a minimum. With further addition of surfactant, frequency decreases, and the decay time slightly lengthens. Above critical micelle concentration, all these parameters stabilize. Interestingly, the critical concentration, at which frequency drop occurs, depends on mode order. This clearly shows that the frequency drop and minimum decay time are not a consequence of some abrupt change of interfacial properties, but are a consequence of some phenomena, which still need to be explained.
Permanent Link: http://hdl.handle.net/11104/0221974