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Experiments of Bubble and Drop Breakup in a Turbulent Flow.
Zedníková, Mária ; Vejražka, Jiří ; Stanovský, Petr
Bubble and drop breakage in a turbulent flow is studied experimentally. In an experimental cell, the turbulent flow (of distilled water) is generated by an array of coaxial nozzles, which allows adjusting independently the turbulence intensity and the mean velocity. Either air or cyclohexane is injected in order to produce bubbles or drops. Their breakage by the turbulent flow is observed using a high-speed camera. The image processing provides information about particles in each image. Tracking software is developed and it allows to identify and characterize the breakup events (their location, number and sizes of daughter particles and also trajectories prior the breakup) and to distinguish them from a simple overlap of multiple bubbles. The parameters characterizing the breakup are then studied in dependence on local flow conditions.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_C22016120713101 - PDF
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Characterization of Turbulent Flow in a Breakup Cell.
Vejražka, Jiří ; Zedníková, Mária ; Stanovský, Petr
Our research focuses on breakup of bubbles and drops induced by a flow turbulence. In this contribution, we describe the experimental setup used for studying the breakup, and we characterize flow within it. The setup is a rectangular glass cell, in which a turbulent flow is generated by a set of coaxial nozzles. The flow within it is characterized by means of particle image velocimetry. From the velocity data, i) local dissipation rate (ε) is estimated using Large-Eddy PIV method, and ii) statistics of velocity difference in two points is evaluated. Estimation of ε is validated by integrating the total dissipation in the setup, which reasonably agrees with the injected kinetic energy. The probability density function of velocity difference is non-Gaussian and when properly normalized, it is universal within the setup.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22016120713100 - PDF
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Disposal of Radioactively Contaminated Ion Exchangers by Molten Salt Oxidation – Preliminary Results of the Project.
Pohořelý, Michael ; Šyc, Michal ; Stanovský, Petr ; Stoklasa, J. ; Karásková Nenadálová, L. ; Pražák, P. ; Svoboda, Š. ; Grič, L. ; Fabián, P.
In the contribution, there are summarized significant fuel-energy properties of selected ion exchangers (Purolit A-400 MB OH a Purolit C-100 H) and important properties of suitable melts for process MSO.
Fulltext: content.csg - PDF
Plný tet: SKMBT_22316060713521 - PDF
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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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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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