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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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Influence of Interphase Meniscus on Bubble Formation at a Plate
Stanovský, Petr ; Růžička, Marek
This work is focused on a single bubbling from orifice at the plate as the first step for modelling of multi-orifice bubble formation at perforated plate. We explored experimentally an influence of design parameters (orifice diameter, plate thickness, liquid viscosity, gas chamber volume) on the interphase meniscus behaviour. The influence of an external acoustic field on the meniscus and bubble formation was explored also to simulate an influence of the sound field produced by other bubbles in real process. Acquired characteristics of the meniscus were incorporated into the model of bubble formation process.
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Experimental Study of Bubble Interactions with the Solid Surface
Zedníková, Mária ; Vobecká, Lucie ; Vejražka, Jiří ; Růžička, Marek
The experiments were carried out in a rectangular vessel equipped with a device generating the bubbles of defined size ranging from 0.4 to 2.0 mm (Vejrazka et al., 2008). Cleaned glass was used as a hydrophilic surface and polypropylene, polyethylene and Teflon were used as hydrophobic surfaces. Deionised water with addition of sodium dodecyl sulphate was used as liquid. The collision and attachment process was observed by means of high speed camera. The following quantities were evaluated from the image sequences: impact and rebound velocities of a bubble, maximal bubble deformation during the contact with the surface and the time required for three-phase contact line formation. The experimental results were compared with our previous investigations (Fujasova-Zednikova et al., 2009).
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Research of Multiphase Systems at ICPF AS CR Prague
Zedníková, Mária ; Růžička, Marek ; Drahoš, Jiří
The aim of this contribution is to present to the Czech waste water treatment community the multiphase flow research at the ICPF ASCR. The goal of the research is to understand the basic physical mechanisms of flow systems with two or more phases. The interest covers a broad range of the multiphase flow systems; for instance: production and hydrodynamics of bubbly mixtures, flow regimes and their identification, effect of control parameters on the flow regimes, mass transfer in gas-liquid systems, bubble formation, coalescence and break-up, hydrodynamic interactions of bubbles, interaction of bubbles with solid particles, sedimentation of polydisperse mixtures etc.
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The Study of Interactions of Bubbles with Solid Surface. The Effect of Surfactant Concentration and Type of Solid Surface
Vobecká, Lucie ; Zedníková, Mária ; Vejražka, Jiří ; Růžička, Marek
This contribution deals with experimental study of interactions between a bubble and a solid horizontal surface. The influence of surfactant concentration in liquid and of material of the solid surface on the interaction is observed. It is observed that the material of solid surface has not significant influence on the hydrodynamics of impact of bubble on a wall. The impact velocity is not affected by surfactant presence because the liquid flow around the bubble moves adsorbed surfactants to rear of the bubble and the interface at top of the bubble stays mobile. The presence of surfactant has strong effect on the bubble rebound, as the rebound velocity and the maximal distance of bubble from the wall decreases with increasing surfactant concentration. No bubble rebound is observed at high concentration of surfactant.
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Hydrodynamika bubliny narážející na stěnu. Experiment a modelování
Zedníková, Mária ; Vejražka, Jiří ; Růžička, Marek ; Drahoš, Jiří
The contribution deals with both experimental and theoretical investigation of collision of a bubble with a horizontal hydrophobic (glass) surface. The terminal bubble velocity, impact velocity, contact time of bubble with the wall and restitution coefficient (ratio of restitution and terminal velocity) are evaluated (by means of a high-speed camera) as a function of bubble size, which is ranging from 0.34 to 2.07 mm. The experimental results are compared with the models based on a balance of forces acting on a bubble during the interaction process. A good agreement is showed between the experimental data and theoretical predictions.
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Hydrodynamika bubliny narážející na stěnu, experiment a modelování
Zedníková, Mária ; Vejražka, Jiří ; Růžička, Marek ; Drahoš, Jiří
The contribution deals with both experimental and theoretical investigation of collision of a bubble with a horizontal hydrophobic (glass) surface. The terminal bubble velocity, impact velocity, contact time of bubble with the wall and restitution coefficient (ratio of restitution and terminal velocity) are evaluated (by means of a high-speed camera) as a function of bubble size, which is ranging from 0.4 to 1.1 mm. The experimental results are compared with the models based on a balance of forces acting on a bubble during the interaction process. A good agreement is showed between the experimental data and theoretical predictions.
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