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Formation and evolution of dynamical binaries
Pavlík, Václav ; Šubr, Ladislav (advisor) ; Heyrovský, David (referee)
The aim of this work is the study of hard binary stars in the star cluster and their time of life before they crossed the energetic boundary, which separates the soft and hard binaries. We used our own method of identification of binary stars within the model of star cluster which is based on the given positions, velocities and masses of stars. This method uses three main criteria -- the proximity of two stars, the time that this pair was found together and negative total energy. The results that we obtained using our algorithm helped us to determie more precise boundary between the hard and soft binary than the analytical estimates based on the evaluation of the typical kinetic energy of the free stars within the cluster. We also studied the lifetime of the binaries before they become hard and we reached a correspondence with the results of Tanikawa et al. (2011), who studied similar topic. Due to a large set of numerical realizations, which we analysed, we got better statistics than previous works. We also found that the examined lifetime of binaries seems to be represented by exponential distribution. For better analysis of this distribution it would be necessary to use about five times higher time resolution than we worked with.
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The dynamic characteristics of check valve
Pavlík, Václav ; Dokoupil, Pavel (referee) ; Habán, Vladimír (advisor)
This master´s thesis provides an overview of all designs of check valves, their usage and typical features. Main purpose of this work is to clear up the phenomenon of check valve slam and the other problems that occur during transients. The check valve slam was measured at the test rig in the hydraulic laboratory. For unsteady flow evaluation after pump shut down was used Gibson method. The dynamic characteristic was possible to create by results from this method. It was achieved without impact of the speed of sound in the fluid. This work also contains 2D transient CFD calculations, which was used for evaluation of the hydrodynamic torque acting on the hinge pin. This approach provides an option to calculate wide range of cases at the expense of not entirely exact geometry. The main contribution of the theoretical study at the beginning of this thesis is its entireness. It might give an important clue when right valve is selecting. For good choice of valve might be helpful to use dynamic characteristics in this thesis presented. Mentioned characteristics were created by new way and its background is in measurements and simplified CFD calculations.
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High pressure hydraulics in agricultural machinery
Pavlík, Václav ; Kárník, Jan (referee) ; Soukup, Lubomír (advisor)
This bachelor thesis provides an overview of the most used ways of converting kinetic energy into pressure energy and the other way around by using hydrostatic converters. It is focused on the issue of high-pressure hydraulic mechanisms in agricultural machinery. In the next section I focused on getting an overview of the function of sophisticated hydraulic systems in current tractors and calculation of heat losses of lifting weight by front three-point hitch. For solving was used Bernoulli equation for real flow in pipes.
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