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Mixed-flow submersible water pump driven by hydrostatic motor
Para, Marcel ; Ranuša, Matúš (referee) ; Nevrlý, Josef (advisor)
Bachelor thesis solves the problem of a submersible, diagonal hydrostatic pump. This study describes the basic principles of hydraulics and equipment. The possibility of engaging the hydrostatic system as an amphibious vehicle is investigated in the Bachelor thesis. The work is written in cooperation with the sponsor of HYDRAULIC RESEARCH CENTRE, spol. S.r.o., which is part of SPL Holding., Inc.
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Controllability assessment of the Roudnice nad Labem sector weir box at extreme floods
Růžek, Patrik ; Haluza,, Miloslav (referee) ; Šulc, Jan (advisor)
This thesis deals with the determination of the load torque during flood conditions on the hydrostatic sectoral weir in Roudnice nad Labem. Problems are solved due to a glitch in the lowering sector. The aim of this study is to determine the resulting torque, of three selected states, which occurred at the water works. The issue was solved as a plane 2D problem using AutoCAD, in which were read the relevant data. It was also used ANSYS software, which modeled the flow of water over the weir to detect pressures acting on overflow face. All calculations are then counted in Microsoft Excel. Force balance is performed on the one-meter design.
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Actions on bridges caused by the water flow and floating items
Řezník, Jindřich ; Duchan, David (referee) ; Špano, Miroslav (advisor)
The subject of this thesis is the enumeration and analysis methods applicable to the calculation of loads on bridges from water and water-borne objects. It involves a hydrodynamics loads, loads from captured debris and from impacts of the individual water-borne objects and their clusters. It includes an assessment of the current situation, the teoretical analysis and model calculations on the concrete bridge with the evaluation of usable methods.
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Supernova driven super star cluster wind
Jeřábková, Tereza ; Wünsch, Richard (advisor) ; Walch-Gassner, Stefanie (referee)
In this thesis we study the interaction of supernova ejecta in the environment of young massive clusters. It has been already shown that winds of massive stars can be thermalized by mutual interactions inside the cluster and drive the strong star cluster wind. The SNe are, as discrete and extremely energetic events, in all ways diferent from the continuous stellar winds. This triggers the question under which parameter and if at all can the SNe ejecta interaction from a smooth star cluster wind. Therefore we at first parametrize the SNe explossions and based on the 3D simulations in FLASH we show for the first time that the convergence of the SNe ejecta interaction to a smooth star cluster wind is controlled by a single parameter ΠSN . The paramater ΠSN estimates the mean number of interacting SN ejecta based on a comparison of supernova rate and crossing time of SN ejecta in a cluster. For high enough values ΠSN > 1 the cluster is able to build up smooth a star cluster wind. This allows us to use a 1D semi-analytic code WINDCALC to calculate the cooling of the hot gas due to dust and estimate under which conditions the SNe-inserted matter is captured. This may explain the origin of so-called anomalous globular clusters. 1
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Hydrodynamic and thermal mode ling of reactive flow in the surroundings of intrusions
Jandová, Tereza ; Dolejš, David (advisor) ; Bruthans, Jiří (referee)
English Summary Intrusion of magma into the Earth's crust is associated with significant thermal perturbations, release of aqeuous fluids and formation of hydrothermal system. In order to better understand the feedback relationships between fluid flow, thermal evolution and permeability variations, we have modeled conductive and advective cooling of a shallow- crustal pluton using the SHEMAT software. Our model represents a two-dimensional cross section through the lithosphere with homogeneous material properties, whebery the heat and mass conservation equations are solved by finite difference method. We first calculate the stable lithospheric geotherm by emplying constant basal thermal flow of 40 mW m-2 and a constant surface temperature. Subsequently, we consider a rectangular magmatic intrusion emplaced at 5-10 km depth, which forms a contact aureole by conductive cooling. With time, a mushroom-like shape of the contact aureole is predicted. Inclusion of aqueous fluid flow into the model causes only a small alteration of thermal evolution mainly because the permeability is low and the fluid mass is negligible due to very low density under hydrothermal conditions. In addition to thermal effects, we have explored variations in hydraulic head in order to address the ensuing effects on the flow velocity. The...
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Early phases of formation and evolution of planetary systems
Chrenko, Ondřej ; Brož, Miroslav (advisor) ; Kley, Wilhelm (referee) ; Morbidelli, Alessandro (referee)
We study orbital evolution of multiple Earth-mass protoplanets in their natal protoplanetary disk. Our aim is to explore the interplay between migration of protoplanets driven by the disk gravity, their growth by pebble accretion, and accretion heating which affects gas in their neighbourhood. Radiation hydrodynamic (RHD) simulations in 2D and 3D are used to model the problem. We find that the heating torque, i.e. the torque exerted by asymmetric hot underdense gas near accreting protoplanets, significantly changes the migration. Specifically, it excites orbital eccentricities of migrating protoplanets, thus preventing their capture in chains of mean-motion resonances. The protoplanets then undergo numerous close encounters and form giant planet cores by mutual collisions. Additionally, if inclinations also become excited, we describe a new mechanism that can form binary planets by means of consecutive two-body and three-body encounters, with the assistance of the disk gravity. Finally, our 3D RHD simulations reveal a complex distortion of the gas flow near an accreting protoplanet, driven by baroclinic perturbations and convection. For specific temperature-dependent opacities of the disk, an instability is triggered which redistributes gas around the protoplanet and leads to an oscillatory migration,...
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Theoretical preparation for the Comparison of efficiency of selected types kayaking paddles in forward stroke.
Vašina, Jiří ; Bílý, Milan (advisor) ; Kubový, Petr (referee)
Title: Theoretical preparation for the Comparison of efficiency of selected types kayaking paddles in forward stroke. Objectives: Objetcive for this study is to make a research study for paddle blade force expereminet by searching and treatment of studies which aim on similar topic. Methods: Research and treatment of foreign and czech studies. The information has been achieved trought combination of the direct, indirect and progressive methods. Conclusion: Parts of the study contain a treatment of foreign and czech studies with theoretical preparation for next experiment. Keywords: Biomechanics, strain gauge, slalom paddle, stroke, hydrodynamics
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Controllability assessment of the Roudnice nad Labem sector weir box at extreme floods
Růžek, Patrik ; Haluza,, Miloslav (referee) ; Šulc, Jan (advisor)
This thesis deals with the determination of the load torque during flood conditions on the hydrostatic sectoral weir in Roudnice nad Labem. Problems are solved due to a glitch in the lowering sector. The aim of this study is to determine the resulting torque, of three selected states, which occurred at the water works. The issue was solved as a plane 2D problem using AutoCAD, in which were read the relevant data. It was also used ANSYS software, which modeled the flow of water over the weir to detect pressures acting on overflow face. All calculations are then counted in Microsoft Excel. Force balance is performed on the one-meter design.
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Magnus force acting upon a rotating sphere passing in an incompressible viscous flow
Beck, Dominik ; Martinec, Zdeněk (advisor) ; Čadek, Ondřej (referee)
Classical results of hydrodynamics such as Stokes' force law and Kirchhoff's mo- ment (torque) law are re-derived for laminar viscous flow in the framework of modern compact simplified vector calculus notation. First perturbations of these laws are found and compared visually with experiments. The Magnus drag force on a rotating and moving sphere surrounded by an incompressible viscous New- tonian fluid is derived from the perturbation series of the Navier-Stokes equations in low speed regimes with a small Reynolds number.
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Hydrodynamic and N-particle simulations of asteroid collisions
Ševeček, Pavel ; Brož, Miroslav (advisor) ; Wünsch, Richard (referee)
We study asteroidal breakups, i.e. fragmentations of targets, subsequent gravitational reaccumulation and formation of small asteroid families. We fo- cused on parent bodies with diameters Dpb = 10 km. Simulations were per- formed with a smoothed-particle hydrodynamics (SPH) code combined with an efficient N-body integrator. We assumed various projectile sizes, impact veloci- ties and angles (125 runs in total). Resulting size-frequency distributions are sig- nificantly different from results of scaled-down simulations with Dpb = 100 km targets (Durda et al. 2007). We thus derive new parametric relations describing fragment distributions, suitable for Monte-Carlo collisional models. We also characterize velocity fields and angular distributions of fragments, which can be used in N-body simulations of asteroid families. Finally, we discuss several uncertainties related to SPH simulations.
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