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Oscillation of Interfacial Meniscus during the Formation of Bubbles
Stanovský, Petr ; Růžička, Marek
A closer look at the interphase meniscus in the model system with a transparent plate using a high-speed camera has showed that after detachment of the bubble the meniscus moves to the lower orifice rim. On that rim the meniscus oscillate dumped by increasing pressure in the space below the plate. In the description of the bubble growth at the orifice during so called waiting period accrue the equations describing the oscillatory behavior of the meniscus. Together with the nonlinear Rayleigh-Plesset equation it results in a bifurcation behavior - the volume of bubbles differ by up to 50% from the mean at certain values of the gas flow. This phenomenon has not been previously identified as the time-averaged values of bubble sizes conceal this effect.
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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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Parameters Affecting Process of Particles Sedimentation: III
Kulaviak, Lukáš ; Růžička, Marek ; Drahoš, Jiří ; Hladil, Jindřich
The aim of our contribution is to study the effect of the particles properties on their settling behaviour in solid-liquid suspensions. Generally, the particles interact mutually in a complex way. They are also coupled with the motion of the liquid whose flow they generate. The resulting behaviour depends on many mechanical particle properties (roughness, shape, size, abrasive hardness, texture, fine particle presence) and electrochemical properties of the interface between the particles and water (surface tension, zeta-potential, electrostatic potential, etc.).
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