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Large Eddy Simulation of Turbulent Two-Phase Flow
Volavý, Jaroslav ; Fürst, Jiří (referee) ; Vimmr, Jan (referee) ; Jícha, Miroslav (advisor)
Doctoral thesis deals with the numerical simulations of two-phase flows, especially with prediction of movement of dispersed phase (particles) carried by fluid. The Euler-Lagrange approach was applied for description of the system fluid-particles. It means that the fluid is considered to be continuum and its movement is described using Euler approach. Particles are regarded as mass points and their movement is solved using Lagrangian approach. The Large Eddy Simulation method was adopted for solution of the fluid flow. The series of simulations of the backward-facing step flow laden with particles were performed. The concentration of the particles in the flow was high enough for consideration of the influence of particles on the turbulence of the carrier phase. The developed scheme for generation of turbulence on the inlet is applied. The influence of anisotropic decomposition of subgrid energy on movement of particles was studied in the frame of this work.
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Experiments critical heat flux
Štaffa, Petr ; Martinec, Jiří (referee) ; Suk, Ladislav (advisor)
The Bachelor’s thesis deals with phenomenon of critical heat flux in a core of nuclear reactor. The first part is dedicated to describe physical nature of critical heat flux and basic thermo mechanical and hydrodynamics terms. The second part is dedicated to summarize experimental investigations on critical heat flux and their process.
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Some results of theoretical and experimental studies on slurry flows of coarse solid materials in vertical pipelines
Berman, V. ; Kril, S. ; Vlasák, Pavel
The paper presents the results of theoretical and experimental investigations of the pressure gradient for flow of a mixture of large solids particles and water in straight vertical pipelines. The mathematical model of vertical two-phase flow was developed. Based on the developed model and experimental data of the solid particles liquid and liquid relative velocity, the functional dependence of the pressure gradient on the corresponding parameters was derived. This method was generalized for hydraulic transport of a broad category of solid particles conveyed in water as a function of the average size and concentration. Comparisons of our computations with experimental data for the corresponding pressure gradients are also presented.
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Analysis of Shook-Gillies model using radiometrically measured concentration profiles in settling-slurry pipe
Pěník, Vojtěch ; Matoušek, Václav ; Krupička, Jan
In 1994, R.G. Gillies and C.A. Shook published their predictive model for concentration profiles in pipe flows of heterogeneous settling slurries. The model has not been validated in the literature yet. In this paper, the model is analysed and compared with own concentration profiles measured using a radiometic device presented at the last Symposium on Anemometry. The results show that key parameters of the model are insufficiently evaluated and their use in the model rather unclear. The model should be validated using a representative database of experimentally determined concentration profiles. On this base, the key parameters in the model should be specified in more details.
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Further developements in radiometric method for measurement of slurry density distribution in pipe flow
Krupička, Jan ; Matoušek, Václav ; Pěník, Vojtěch
Laboratory test loop for slurry pipe experiments at the Institute of Hydrodynamics is equipped with two prototypes of radiometric devices which are in permanent evolution as well as the radiometric method of measurement and data processing. Effect of usage of collimated gamma-ray source on the spatial resolution of the radiometric method is studied in this article. Up to now, four differend versions of image reconstruction methods were used to evaluate concentration distribution in a pipe cross-section. Comparison of these methods is presented based on experimental data.
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Experiments on Large Bubbles Rising in an Inclined Flat Channel
Tihon, Jaroslav ; Pěnkavová, Věra ; Vejražka, Jiří
The motion of single air bubbles in an inclined flat water channel is investigated experimentally. The electrodiffusion technique of near-wall flow diagnostics is applied to measure the wall shear stress distribution under large bubbles rising along the upper channel wall. The directionally sensitive, two-strip electrodiffusion probes are used to detect the location of flow reversal in a thin liquid film separating the moving bubble from the wall. The electrodiffusion measurements are synchronized with the visual observation of bubble movement done by a high-speed camera. The experiments are carried out for three different channel heights (1.5, 4, and 8 mm) and cover a wide range of channel inclination angles (from horizontal to vertical position). The experimental results on bubble motion characteristics obtained in stagnant and co-flowing liquid arrangements are confronted with the recent predictions and scaling provided by theoretical models.
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Numerická simulace separovaného dvoufázového proudění vařící se vody v kanálu o tvaru cívky
Novák, Aleš ; Hrubý, Jan
This work deals with a quasi-1D mathematical model of flow of a boiling liquid-vapor mixture in a coil-shaped duct heated from the outer side of the coil. The liquid and gas phases are allowed to flow at different velocities (stratified flow regime). The model simulates a modification of the laboratory steam generator built in Institute of Thermomechanics AS CR. The liquid is centrifuged to the heated wall thus enhancing the heat transfer. The model also includes heat conduction in the metal body of the steam generator.
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