|
| |
|
|
Oscillations of Bubbles Attached to a Capillary: Case of Pure Liquid
Vejražka, Jiří ; Vobecká, Lucie ; Tihon, Jaroslav
In this contribution, we therefore present results of a linear inviscid theory for shape oscillations of a spherical bubble, which is in contact with a solid support. The theory allows determining eigenmode, but also response of the bubble shape to a motion of its support or to volume variations. Present theory covers also the cases previously analyzed by Strani and Sabettaand Bostwick and Steen, and it can be applied to both bubbles and drops. The theory has been compared to experiments. Good agreement is found for the case of small bubbles, which have spherical static shape. Experimental results for larger bubbles and drops deviate from the theory, if a neck is formed. It is shown that this deviation correlates well with a ratio of bubble volume to the maximum volume, when a detachment occurs.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_C22012112614031 - PDF
|
|
| |
|
|
Oscillations of a Bubble Attached to a Capillary Tip
Vejražka, Jiří ; Vobecká, Lucie
The contribution provides a procedure for computing the eigenmode frequencies, shapes and dampings for the case of oscillations of a bubble or drop attached to a capillary tip. The procedure is based on the analysis of Bostwick and Steen, but its results are recast to a more convenient and more compact form. Analytical results are in a good agreement with experiments, if the bubble size is sufficiently smaller than the size at detachment due to Archimedes forces.
Fulltext: PDF
|
|
|
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.
|
|
|
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.
|
|
|
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).
|
|
| |
|
|
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.
|
|
| |
guest ::
