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Interaction of laser beam and tracer particles in liquid helium
Hodic, Jan ; Skrbek, Ladislav (advisor) ; Schmoranzer, David (referee)
The thesis resums the base knowledges of the domain of the fluid mechanics, deduction of the Navier-Stokes equations, introduction of the Reynolds number and its difference and a fundamental deduction of the Stokes formula, expressing a depending of the resistance of a fluid on a moving sphere. There are the problematic of turbulence including of energetical spectrum by Kolmogorov, cascade mechanism of disintegration of vortices and Kolmogorov length analysed too. There are introduced vorticity and Rayleigh number the exploration of the classical turbulence using liquid helium 4 in this thesis. There are stated the basical physical possesions of the helium 4 here, including of its phase diagram and double- componental model. Special chapture pays attention to the hydrodynamics o helium 4, especially to the relation from pressure to temeprature. After it comes introduction to quantum turbulence, including of the basical formulae and description of the used experimental method of the partical tracker, as well asthe basical motivation of the problem. There is calculated an approximate calculation of the interaction between a particle and a laser beam, as well as an exact calculation for a spherical particle. During the calculation is presumed uncompressible, non-vorticose flowing, using basical formulae for...
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Temperature Inversion and Heat Transport Against the Temperature Drop in Two-Phase Convection of Cryogenic Helium
Urban, Pavel ; Schmoranzer, D. ; Hanzelka, Pavel ; Skrbek, L.
In the system of two bodies A and B connected by a two-phase vapour-liquid system consisting only of cryogenic helium, we observed anomalous heat transport from the colder but heated body B to the warmer but cooled body A. We noticed this effect during the process of liquid evaporation inside a cylindrical pressure convection cell used for study of Rayleigh-Bénard convection. This anomalous heat transfer occurs under non-equilibrium conditions, owing to the phase transitions that take place inside the cell while temperature inversion develops between the heated but cooler bottom plate and the cooled but warmer top plate. This process is, by virtue of the system being open with respect to heat transport, in no contradiction to the second law of thermodynamics, and a numerical model was formulated that describes the observations with good agreement.
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