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Analysis of the impact of the conic aperture placement in the supersonic flow in the differentially pumped chamber
Rous, Miroslav ; Bílek, Michal (referee) ; Maxa, Jiří (advisor)
The thesis is focused on the medium dynamics simulation in the environmental scanning electron microscope. Specifically, it researches (examines) the conical aperture location effect in the differential pumped chamber and the width of the pumping channel in this chamber. The theoretical part deals with the environmental scanning microscope generally and other tools used in this thesis, e.g. ANSYS Fluen software, fluid turbulence, medium free path of molecules and electrons scattering. In the practical part, the work is focused on data processing from the ANSYS Fluent program and on their evaluation.
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Analysis of the shape of the intake ports of the current concept differentially pumped chamber
Bílek, Michal ; Vyroubal, Petr (referee) ; Maxa, Jiří (advisor)
This master´s thesis discusses the analysis of the shape of the intake ports of differentially pumped chamber for the current concept. The first part is an introduction to the microscopy issue, then it is focused on ESEM microscopes and it also includes a describtion of the Flow dynamics and a mathematical describtion. In the following chapters the software Solid Works, where the model of differentially pumped chamber is created, and the software Ansys Fluent, which is used for analysis, are described. The second part concerns the proposed concepts and the results of their simulations. At the end of the work the results are analyzed and evaluated.
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Computational modelling of aerodynamic noise caused by the car’s side mirror
Vobejda, Radek ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
The master’sthesis deals with numerical modelling of aerodynamic noisewhich arisesinside of the carcabin. In the first part ofthe thesis simplified model of geometry of the car and of the inside acoustic pressure arecreated. After that numerical analysis of created models of geometry are doneandvarious models of turbulenceare discussed. The results of these CFD simulationswhere then used for changing the model of geometry of the wing mirror. Outputs of these simulations were used for solving the numerical analysis of noise in the car cabin.
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Assessment of ventilated floors construction
Jurka, Jiří ; Kmínová,, Hana (referee) ; Šilarová,, Šárka (referee) ; Šťastník, Stanislav (referee) ; Škramlik, Jan (advisor)
Air insulation, especially its efficiency, is often underestimated and most often it is recommended as combination of several methods by our experts. It is known that flowing air used to eliminate excessive humidity in lower construction is insignificantly promoted. Already our ancestors in ancient Rome had experience with implementation of air insulations. However, nowadays such design is connected with many doubts and it forces us to use sense, especially knowledge of construction physics. So it urges higher technical precision when designing functional ventilation system. Each building is actually a unique object, with regard to its position and used properties, that is why certain natural conditions must be accepted when designing. It is more complicated and figuratively speaking it can be written in c. 20 equations of twenty unknowns. Other problems arise in unknown coefficients to individual parameters and their effects. From another point of view it is the issue of changing air during the day, passing fronts, annual cycles and all of these in relation to internal environment of the building, materials used in the construction, land properties of rocks, and last but not least, relation to the terrain around the building. Then there are the effects of the building's altitudes etc. In total they are cycles with sine character of dampening and drying. The thesis discusses how to test the functionality of AIR insulations designed for the floor ventilation in historic buildings and follows on from the previously published articles. A flow analysis is being performed on an object of the city of Žirovnice which has been registered in the list of cultural monuments and was built as a brewery in the years 1589-1592 on the site of an older medieval building. This article brings new air-flow element. The aim of the article is to analyse in detail the air flow in a specific floor void with the aid of modern CFD programs and experimental measurements using the ALMEMO
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Monitoring and Simulation of ADS Experimental Target Behaviour, Heat Generation, and Neutron Leakage
Svoboda, Josef ; Kliman,, Ján (referee) ; Wagner,, Vladimír (referee) ; Katovský, Karel (advisor)
Urychlovačem řízené podkritické systémy (ADS) se schopností transmutovat dlouhodobě žijící radionuklidy mohou vyřešit problematiku použitého jaderného paliva z aktuálních jaderných reaktorů. Stejně tak i potenciální problém s nedostatkem dnes používaného paliva, U-235, jelikož jsou schopny energeticky využít U-238 nebo i hojný izotop thoria Th-232. Tato disertační práce se v rámci základního ADS výzkumu zabývá spalačními reakcemi a produkcí tepla různých experimentálních terčů. Experimentální měření bylo provedeno ve Spojeném ústavu jaderných výzkumů v Dubně v Ruské federaci. V rámci doktorského studia bylo v průběhu let 2015-2019 provedeno 13 experimentů. Během výzkumu byly na urychlovači Fázotron ozařovány různé terče protony s energií 660 MeV. Nejdříve spalační terč QUINTA složený z 512 kg přírodního uranu, následně pak experimentální terče z olova a uhlíku nebo terč složený z olověných cihel. Byl proveden také speciální experiment zaměřený na detailní výzkum dvou protony ozařovaných uranových válečků, z nichž je složen spalační terč QUINTA. Výzkum byl především zaměřen na monitorování uvolňovaného tepla ze zpomalovaných protonů, spalační reakce a štěpení, způsobeného neutrony produkovanými spalační reakcí. Dále se na uvolňování tepla podílely piony a fotony. Teplota byla experimentálně měřena pomocí přesných termočlánků se speciální kalibrací. Rozdíly teplot byly monitorovány jak na povrchu, tak uvnitř terčů. Další výzkum byl zaměřený na monitorování unikajících neutronů z terče porovnávací metodou mezi dvěma detektory. První obsahoval malé množství štěpného materiálu s teplotním čidlem. Druhý byl složený z neštěpného materiálu (W nebo Ta), avšak s podobnými materiálovými vlastnostmi se stejnými rozměry. Unik neutronů (resp. neutronový tok mimo experimentální terč) byl detekován uvolněnou energií ze štěpné reakce. Tato práce se zabývá přesným měřením změny teploty pomocí termočlánků, s využitím elekroniky od National Instrument a softwaru LabView pro sběr dat. Pro práci s daty, analýzu a vizualizaci dat byl použit skriptovací jazyk Python 3.7. (s využitím několika knihoven). Přenos částic by simulován pomocí MCNPX 2.7.0., a konečně simulace přenosu tepla a určení povrchové teploty simulovaného modelu bylo provedeno v programu ANSYS Fluent (pro jednodušší výpočty ANSYS Transient Thermal).
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Influence of nozzle angle on gas pressure distribution in the nozzle according to Prandtl's theory
Dostalová, Petra ; Maxa, Jiří (referee) ; Šabacká, Pavla (advisor)
The thesis is focused on issue pressure distribution in the nozzle while pumping the differential pumped chambre of an environmental scanning microcope. The main task of the thesis is to find suitable design of this nozzle respect to Prandtl`s theory. In the theoretical part, there are presented microscopy as science. Afterwards the thesis is focused on environmental scanning electron microscopy and its problem and vacuum system, computer program used for preparation of simulation and study that the experimental part is based on. The experimental part evaluates the results of physical-mathematical analysis of the flow inside and behind the Laval nozzle in the experimental chambre. The results are the basis for the optimal proportions of this nozzle.
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Design optimization of water-cooled thermocouple probe
Dohnal, Miloslav ; Vondál, Jiří (referee) ; Hájek, Jiří (advisor)
The object of this bachelor’s thesis is to create a computational model of an existing (basic) structure water-cooled thermocouple probe, to calculate and evaluate the quality of existing cooling probe and to propose possible design modifications to improve the cooling effect of the probe tip. Verify and evaluate design modifications by further calculation. The calculation will be carried out using computational fluid dynamics (CFD method). On the contrary, the aim of this work is not to create another text tool for students dealing with CFD topics. The first part describes the meaning and history of the CFD methods, then mentions the work on the principle of thermocouple probes and its application in practice. The second part of the work is devoted to problem solving. It describes the reason for the introduction of model situations when calculating the cooling effect of thermocouple probes and calculation indicates what type of flow occurs inside the thermocouple probe. It further describes the results of calculations for several approximations gradually increasing accuracy of the resulting solution of the problem and assessing the quality of cooling in the probe tip current (basic) structure. The final part deals with design changes for better cooling effect especially in the probe tip, which is verified by further calculation as well.
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Analysis of the impact of the baffle placement in the supersonic flow in the differentially pumped chamber
Vlasáková, Martina ; Bílek, Michal (referee) ; Maxa, Jiří (advisor)
This thesis deals with the area of the differential pumping chamber of an environmental scanning electron microscope, engaging the pressure limiting apertures and the influence of the enclosure inside the chamber. In the theoretical part, it is first called Microscopy as science, information about microscopes (division of microscopes) and electrons. Afterwards, the theory deals directly with environmental scanning electron microscopy and its problems and vacuum system, mathematical models and computational areas, basic information about the comparative study from, which the thesis is based. In the experimental part there are presented the objectives of the work and the chapter dealing with the processing of results, which are compared with the initial study using the program Ansys Fluent.
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Flap otpitmization for SKYLEADER aircraft
Kácal, Jan ; Vaněk, František (referee) ; Koutník, Tomáš (advisor)
This diploma thesis focuses on optimization of the flap for the ultralight aircraft Skyleader JA 600, which is produced by the Jihlavan s.r.o. company. Individual types of flaps used in ultralight aircrafts are described in the initial phase of the thesis. In addition, description of the plane of interest Skyleader has been conducted, while along with the basic characteristics the focus is mainly on its wing and flap. The thesis continues with detailed CFD method calibration task, which is mostly focused on the basic turbulent models comparison. The optimization task conducted within this diploma thesis includes CFD calculations to determine aerodynamic characteristics of the flap provided by Jihlavan company, and subsequent determination of its optimal position. An important part of this thesis is also evaluation of the load and strength of the flap in previously determined optimal position. At the end, the strength and fly tests of the flap in the new position are described.
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Stress-strength analysis of an impeller shaft using fluid-structure interaction modelling
Zifčáková, Barbora ; Vondál, Jiří (referee) ; Juřena, Tomáš (advisor)
This master’s thesis deals with numerical simulations of type FSI (Fluid Structure Interaction). Software used is ANSYS Fluent and ANSYS Mechanical. The aim of this thesis is to study the interaction between fluid flow in the mixing tank used in pharmaceutical industry to process eggshells and the agitator whose shaft has deformed during operation. CFD part consists of both one-phase and multi-phase transient simulations. The impact of solid body deformation on fluid flow is neglected hence only one-way Fluid Structure Interaction is considered for the simulations. Fluid flow in the tank and stress-strain behavior of the shaft is evaluated both in quasi-steady state and during start-up of the device. Computations showed that the impact of eggshells on agitator is negligible during operation (in quasi-steady state) unlike the behavior during start-up of the device when stresses and strains of the shaft are significantly higher. Possible reasons why the shaft deformed are presented and further numerical simulations are discussed and suggested.
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