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Dynamics of Shape Oscillations of a Bubble Attached to a Capillary Tip
Vobecká, Lucie ; Vejražka, Jiří ; Orvalho, Sandra ; Zedníková, Mária ; Tihon, Jaroslav
The shape oscillations of a bubble, which is attached to a tip of a capillary tube, are studied experimentally. It is observed that the attachment leads to an appearance of an additional low-frequency mode (denoted as mode 1), when compared to standard theories of oscillations of free bubbles or drops. It is observed that the frequency of mode 1 scales with the bubble size as f ~ D^(-2). The oscillation dynamics of a bubble is strongly influenced if some surface active agent is present in the liquid. Due to interfacial elasticity, the surfactants presence in low concentration increases the oscillation frequency. The decay of oscillations is also faster, probably due to an increase of energy dissipation by Marangoni stresses.
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Oscillation of a Bubble in Surfactant Solution
Vobecká, Lucie ; Vejražka, Jiří ; Zedníková, Mária ; Orvalho, Sandra ; Tihon, Jaroslav
The decay of shape oscillations of a bubble in solutions of a soluble non-ionic surfactant are studied by means of high-speed imaging. The oscillations are induced by a sudden motion of a capillary, to which the bubble is attached. The bubble then either detaches or remains attached at the capillary. In both cases, the observed bubble shape is decomposed into eigenmodes (Legendre polynomials). The frequency f and the decay time τ of the lowest oscillation mode are evaluated. Their dependences on the surfactant concentration c, on the bubble size and on the bubble age are studied.
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