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Numerical model of aerosol formation during biomass combustion
Chýlek, Radomír ; Lízal, František (referee) ; Masaryk, Michal (referee) ; Pospíšil, Jiří (advisor)
This thesis focuses on creating a numerical model to describe the thermal impact on biomass with aerosol formation. The model is based on the modification of the network-based CPD model and is intended for simulating the thermal decomposition of biomass. The objective of this work was to verify the functionality of the model and perform comprehensive validation through laboratory measurements. The validation involved analyzing lignocellulosic biomass and its individual structural materials. The validation results confirmed the model’s ability to simulate slow pyrolysis with good agreement with experimental data. Prior research focused on determining the composition of biomass and selecting an appropriate model for biomass combustion/pyrolysis simulation. The thesis also describes other tested approaches and improvements to the CPD model.
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Heat dissipation axially-cooled glassmaking
Hovorka, Martin ; Pospíšil, Jiří (referee) ; Baláš, Marek (advisor)
The presented thesis deals with a numerical simulation of axially cooled glassmaking parison. Several types of cooling channels have been investigated according to its usage in glassmaking process. Software Star CCM+ was used to describe properties throughout the channels and also the parison itself. The main focus of this thesis lies in comparing of temperature fields, cooling effects and cooling intensity among the chosen channel designs. The boundary condi-tions were kept the same accordingly to glassmaking conditions for every design. Some out-puts were transferred to non-dimensional diagrams in order to recalculation pursuant to other boundary conditions. Properties of diffuser channel designs were compared to an experiment. Transient temperature field of the parison were calculated with Ansys APDL in order to de-termine the accumulation and stationary zone of the parison and to verify the boundary conditions for cooling channels.
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Vortex tube
Chýlek, Radomír ; Škorpík, Jiří (referee) ; Pospíšil, Jiří (advisor)
The purpose of this diploma thesis was to find optimal operational parameters of Ranque–Hilsch vortex tube that would give the best results of temperature separation, and to create a numerical model of the device. Firstly, extensive research of current literature was done and analytical model of the tube was created. Then, the numerical model of the vortex tube was designed using Star-CCM+ software. Afterward, best fitting turbulence model was chosen to do the calculation and optimal geometrical parameters of the tube were obtained as a result of CFD simulation. Then, inlet nozzles for the tube were designed and manufactured. Experimental evaluation of the vortex tube and description of its optimal settings form a substantial part of the project. Finally, the data obtained from the experiment were compared to the results of numerical analysis and conclusions were deduced.
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Numerical modeling of the prestress hollow core slabs Spiroll type on the flexural support and the evaluation of the stresses
Kršík, Jakub ; Vejvoda,, Stanislav (referee) ; Kaplan,, Věroslav (referee) ; Křiváková, Jarmila (advisor)
The doctoral thesis describes the possibilities of numerical modelling of hollow core concrete panels, SPIROLL type. The commercial finite element program ANSYS 13.0 is used for the modelling. The focus is on the specific flexural support of the panel and on the distribution of the shear stresses in the panel ribs near the support. The goal is to valid actually used method for homogenization of the panel’s foreheads and its influence on the shear resistance by using four numerical models. The numerical models are compared and verified with two experiments. The first experiment is vacuum loading on the hollow core slab. Second experiment is about shear loading by applying the loading blocks. Four methods for design of hollow core panels are evaluated. It is the method based on main stresses, design according EN 1992 and EN 1168 and Yang’s method of prestress effects transfer. Based on the results, a method of considering flexural support for the evaluation of hollow core panels is proposed.
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Jet Grouting
Kubín, Tomáš ; Boštík, Jiří (referee) ; Glisníková, Věra (advisor)
The aim of this thesis is to describe jet grouting. There are specified base methods of ground improvement and described possibilities of jet grouting. Furthermore thesis is focused on certain constructions and reconstructions in Brno, where this method was used. In detail it is concerned on reconstruction of the palace of Chlumecky, where jet grouting was used as shoring of foundation pit. Next part of this thesis is a numerical model of this foundation pit and comparison of the results from different constitutive models of soil.
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Energy Piles
Buzgóová, Ivana ; Miča, Lumír (referee) ; Boštík, Jiří (advisor)
In the first part of bachelor thesis, a concept of energy pile is explained and also basic information about usage of geothermal energy, montage of pile, its design and the overall operation of the system is shown. Behaviour of axially loaded energy piles is observed in the individual section. In contrast with other foundation structures, energy piles are also under thermal loading. Next, the main factors of pile behaviour are mentioned, the methods of investigation of energy piles (analytical, experimental and numerical) are described and also characteristics, results from the specific studies that were made in different parts of the world under various conditions. In the second part of the thesis, a simple numerical analysis of energy pile is carried out. The simulation of pile is performed in Plaxis 2D. The description of model, calculation phases are discussed along with achieved results and compared with published studies.
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Analysis of factors influencing internal forces in primary tunnel lining and its design
Rozmánek, Filip ; Rychtecký, Josef (referee) ; Chalmovský, Juraj (advisor)
This thesis deals with the mathematical modelling of the primary lining of a tunnel which finds itself in overconsolidated neogenic clay. This type of construction is typically solved by a combination of linear-elastic beams representing sprayed concrete and a linear elastic – perfectly plastic soil material model. Both of these approaches are a simplification of the behaviour of both sprayed concrete and soil. The real behaviour of concrete is nonlinear and time-dependent when it comes to stiffness and strength. In praxis, this issue is solved by implementing phases of young and cured concrete. The real behaviour of soils is, on the other hand, influenced by hardening. The main goal of this thesis is to use an advanced time-dependent elastoplastic material model (The Concrete model) to create shotcrete lining for the Dřevnovice tunnel, built by the Kernbauweise method. A nonlinear hyperbolic soil material model (The Hardening Soil model) is applied to the neogenic clay environment. Various modelling approaches are used to obtain internal forces and deformations of tunnel lining. These approaches are then graphically compared. The last part of this thesis focuses on verifying the primary lining design of a railway tunnel in central Moravia.
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Defects of railway embankments resulting from their widening in the past
Buzgóová, Ivana ; Grepl, Jan (referee) ; Štefaňák, Jan (advisor)
First chapter of this master's thesis describes specific features of railway embankments in the past and it creates basics for appropriate understanding of following parts. Next, historical development of dimensions of railway platform is introduced. Historical development of dimensions is expected to be a possible reason in field of defects of embankments. Separate chapter refers to various locations in Czech republic where defects of railway embankments can be detected. Description contains not only defects of embankments but also ways of rehabilitation that were performed. Subsequently, the methods of rehabilitation of railway embankments are stated in regard to SŽ S4. In second part of the master's thesis, rehabilitation arrangement of particular railway embankment is designed. It is situated in Česká Kamenice in Děčín region. A numerical simulation of embankment is carried out in Plaxis 2D. The description of model and acquired results are given.
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Electro-Magneto-Hydrodynamic Model for Electron Microscopy
Mačák, Martin ; Horák, Vladimír (referee) ; Uruba, Václav (referee) ; Vyroubal, Petr (advisor)
This dissertation thesis deals with the description and development of an electromagneto-hydrodynamic model intended for electron microscopy. The basis of the work lies in the description of characteristic phenomena taking place in electron microscopes with a focus on environmental electron microscopy. The work dealt with a description of the electromagnetic field, supersonic flow of rarefied gas and a motion of relativistic charged particles in a gaseous environment. An electromagnetic model based on the definition of electric and magnetic vector potential was presented and was used for a simulation of an electromagnetic coil. The supersonic flow of a rarefied gas was defined by Navier-Stokes equations. In order to extend their application to low pressures, the boundary conditions for velocity and temperature were modified. Viscosity and thermal conductivity were subsequently introduced as functions of gas pressure. These adjustments were able to describe the effects of lower collision frequency of gas particles. The presented model was used for the analysis of a flow through a separate aperture and a differentially pumped chamber. Furthermore, the model and necessary adjustments for the description of relativistically moving particles were presented. The model was used for the simulation of electron optics. Separate attention was paid to the interaction of charged particles with a gaseous environment. These interactions had a stochastic character and the presented model described both elastic and inelastic collisions. The presented multiphysics model enables the simultaneous simulation of different physical areas and the interactions between them, which leads to a possibility of a more detailed description of processes and to the improvement of environmental electron microscope design.
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Preliminary study of the construction of a tram tunnel in Brno
Kuhajdik, Adam ; Janků,, Hynek (referee) ; Horák, Vladislav (advisor)
The selection of a suitable tunneling technology within the territory of the town has an essential impact on behaviour of surrounding buildings. The thesis presents basic applicable methods. The selected method is simulated in a mathematical model whose input parameters are defined according to geotechnical investigation and by calculating from cone penetration test. Furthermore, the thesis deals with parametric comparisons of a constructional element in dimensioning, horizontal and vertical shift of this element and simplified comparison of steel and concrete prices. This thesis also contains re – comparison of construction behaviour within a model with real deformations which are measured using an inclinometer in situ.
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