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Mixture-Flow in Combustion Chamber
Hrbáček, Jan ; Lempera, Aleš (referee) ; Drápal, Lubomír (advisor)
The Master's thesis deals with the flow of fuel mixture in the combustion chamber and the influence of its geometry on squish generation caused by the compression lift. The thesis introduces design proposals of the geometry of the combustion chamber focusing on the shape of the squish area and their comparison based on the amount of kinetic energy and the velocity profile obtained using 2-D Squish programme calculations.
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Analysis of the Fluid Flow in Pipes Circular and Not Circular Cross-Section With Methods Using Distribution of the Vorticity Density
Soukup, Lubomír ; Kozubková, Milada (referee) ; Matas, Jakub (referee) ; Štigler, Jaroslav (advisor)
The doctoral thesis deals with the analysis of the flow in the circular and not circular cross-section pipes by methods using the distribution of the vorticity density. This analysis is particularly focused on the derivation of the new velocity profiles formulas using the above mentioned method. In this work is presented a historical overview of the derived velocity profiles. This overview of already derived velocity profiles will be a fundamental benchmark for newly derived velocity profiles. These new velocity profiles are derived for the circular and not circular cross-section pipes and the derivation is based on the analogy of electromagnetic induction by using Biot-Savart law. It is necessary to apply this analogy at first on solitary vortex filament. By taking this step is possible to get the value of the induced velocity from one solitary vortex filament. Subsequently it is possible to obtain the value of the induced velocity from the vorticity wall and afterwards from the vorticity density distribution over the cross section. This work contains also the results of the experimental measurements of the velocity profiles, and of the CFD simulations. Experimentally measured results are used besides other for the selecting of the most suitable CFD computational model. Selected CFD model will be subsequently declared as a reference model and the valid velocity profiles for this model will serve with the experimentally measured data as a benchmark for the newly derived velocity profiles.
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DES modelling of the turbulent flow
Benešová, Stanislava ; Brechler, Josef (advisor) ; Dolejší, Vít (referee)
This thesis deals with the study of hybrid RANS/LES methods for modeling of turbulent flow with a focus on the DES method and its modifications. The theoretical part focuses on the description of turbulent flow and classical methods for its modeling. The following describes the hybrid RANS/LES methods, their principles and categories. Finally, the DES method is described in detail together with its improvement in form of DDES and IDDES methods. The practical part is devoted to the testing of DES and DDES on benchmark problems. We describe here used software OpenFOAM and numerical methods used to discretize the equations. One part is devoted to grid generation. The DES and the DDES methods are tested on two benchmarks: flat plate with zero pressure gradient and backward facing step. The simulaton results are compared with experimental data, with a focus on good modeling of the velocity profile near wall, turbulent viscosity and skin friction coefficient. Powered by TCPDF (www.tcpdf.org)
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Numerical Solution of the Three-dimensional Compressible Flow
Kyncl, Martin ; Felcman, Jiří (advisor) ; Dolejší, Vít (referee) ; Brandner, Marek (referee)
Title: Numerical Solution of the Three-dimensional Compressible Flow Author: Martin Kyncl Department: Department of Numerical Mathematics Supervisor: Doc. RNDr. Jiří Felcman, CSc. Abstract: This thesis deals with a fluid flow in 3D in general. The system of the equations, describing the compressible gas flow, is solved numerically, with the aid of the finite volume method. The main purpose is to describe particular boundary conditions, based on the analysis of the incomplete Riemann problem. The analysis of the original initial-value problem shows, that the right hand-side initial condition, forming the Riemann problem, can be partially replaced by the suitable complementary condition. Several modifications of the Riemann problem are introduced and analyzed, as an original result of this work. Algorithms to solve such problems were implemented and used in code for the solution of the compressible gas flow. Numerical experiments documenting the suggested methods are performed. Keywords: compressible fluid flow, the Navier-Stokes equations, the Euler equations, boundary conditions, finite volume method, the Riemann problem, numerical flux, tur- bulent flow
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Turbulent flow suppression in pipe
Jahn, Jiří ; Rudolf, Pavel (referee) ; Štigler, Jaroslav (advisor)
This thesis deals with ways to suppress turbulent flow in pipelines. In the first part various methods of laminarization are presented, when the turbulent flow is transformed into laminar flow, including the results of experiments published by the authors. The next part presents the results from CFD. The calculations were performed for one of the methods mentioned in the first part and the results were compared with each other. In addition, several options have been suggested to improve the original method.
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Pressure losses in heating systems
Švanda, Martin ; Horká, Lucie (referee) ; Počinková, Marcela (advisor)
This diploma thesis deals with pressure losses in heating systems. The diploma thesis is divided into three sections. The first part is theoretical and deals with the occurrence of pressure losses. It discusses the properties of the fluid that affect pressure losses. It also deals with hydrodynamic phenomena, flow distribution, pressure loss distribution and its calculations. The aim of the second part, which is practical, was to create a heating project for a selected object. The object is a two-floor kindergarten building located in Velké Němčice. For this project, two heating variants were created. For the first variant, radiators and heating benches were designed and for the second variant, underfloor heating was installed in the building. The goal was to use a source which will gain heat mainly from renewable sources, so the air / water heat pump was chosen as the source of heat production. The project ends with a technical report. The third part of the thesis is dedicated to an experiment which purpose was to find out how the pressure losses of the connecting pieces are reacting to the change with the change of the heating water conditions (flow, temperature). Alongside, two pipes were created which differed in the type of connecting pieces so it allowed to compare how their pressure losses differ. Both pipes were connected by radial pressing, but the fittings differed in the quality of the brass, and therefore in the construction. Also, part of the experimental section of the diploma thesis is a description of the course of radial pressing of fittings from the Herz company.
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Fluid flow in narrow gap between two cylinders induced by pressure gradient
Bartková, Tamara ; Štefan, David (referee) ; Štigler, Jaroslav (advisor)
Diplomová práca je zameraná na popísanie prúdenia tekutiny medzikruhovým potrubím. Tok tekutiny je skúmaný pri viacerých podmienkach, čo vedie k laminárnemu ale aj turbulentnému prúdeniu. Práca obsahuje rešeršnú časť, ktorá opisuje doteraz známe vzťahy popisujúce daný typ prúdenia a takisto skúma spôsoby merania rýchlostného profilu v medzikruhových medzerách. Nasledujúca časť obsahuje návrh výpočtového modelu, popis simulácií prúdenia pri konkrétnych podmienkach a ich vyhodnotenie. Výsledky zo simulačnej časti sú použité pri popise charakteristických vlastností turbulentného prúdenia v medzikruží. Tieto charakteristiky sú použité v ďalšej časti práce, ktorá je cielená na získanie analytického vzťahu, ktorý by popisoval časovo stredovaný rýchlostný profil turbulentného prúdenia v medzikruhovej medzere.
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Discharge coefficients for nozzles of a low-NOx gas burner
Zifčáková, Barbora ; Bojanovský, Jiří (referee) ; Juřena, Tomáš (advisor)
Nozzles belong to the main parts of a low-NOx gas burner. Their purpose is to transport fuel into a combustion system. One way of judging a quality of a nozzle is to define its discharge coefficient. It expresses an efficiency of energy conversion – from pressure to kinetic energy. In this thesis the discharge coefficients of several nozzles were established, using Ansys Fluent software for computer simulation. A calculation was tuned to a reference geometry and then applied to other geometries of nozzles, which were both planar and spatial. Numerically obtained data were compared with experimental data. The benefits of this thesis are comparism of two main methods of flow modelling (Scalable Wall Function and Enhanced Wall Treatment) and formulation of a calculation methodology for this type of physical problem. The results provided by this thesis might be used for both another study and experimental research.
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