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Zedníková, Mária ; Vejražka, Jiří ; Stanovský, Petr
A model is developed for predicting the outcome of breakup of a fluid particle (bubble or drop), which is initially deformed (e.g. due to turbulence) and breaks into two daughter particles. An initially dumbbellshaped deformation of the particle is assumed. The evolution of sizes of particle subparts is calculated using RayleighPlesset equations, which consider the inertia of surrounding fluid, capillary action and viscous effects. The redistribution of internal fluid in the particle is calculated using Bernoulli equation. The model computes the sizes of daughter particles after the breakup. By assuming various initial conditions (various initial shapes and initial velocities of deformation), the size distribution of daughter particles is obtained. These size distributions are qualitatively compared with available experimental data and reasonable agreement is observed. Because of strong assumptions, this model cannot be used directly for accurate prediction of size distribution after a breakup. However, it provides an insight in the physics of the breakup, especially on the effect of inner phase properties.
Fulltext: content.csg  PDF Plný tet: SKMBT_C22017030713510  PDF


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 highspeed 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


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 LargeEddy 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 nonGaussian and when properly normalized, it is universal within the setup.
Fulltext: content.csg  PDF Plný tet: SKMBT_C22016120713100  PDF

 

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 fuelenergy properties of selected ion exchangers (Purolit A400 MB OH a Purolit C100 H) and important properties of suitable melts for process MSO.
Fulltext: content.csg  PDF Plný tet: SKMBT_22316060713521  PDF

 