|
|
Low-range high-speed optical transceiver
Pučálka, Jan ; Tošovský, Petr (referee) ; Kubíček, Michal (advisor)
The diploma thesis deals with description and design of a low-cost free-space optical (FSO) link. First, general FSO theory is discussed including their common parameters, properties and topologies. Further, optical signal sources and detectors are proposed. Finally, the selected implementation is described including its design and realization. The proposed FSO consists of two identical segments (modules) to form a full-duplex link. The FSO utilizes LED as a light source, maximum speed data rate is 100 Mb/s with 100Base-TX interface.
|
|
|
Study of heat transfer by turbulent flow in cold helium gas in experiment with Rayleigh-Bernard convection at ISI CAS in Brno
Balko, Marek ; Štigler, Jaroslav (referee) ; Macek, Michal (advisor)
The diploma thesis deals with the study of Rayleigh-Bénard convection for Rayleigh numbers in the range 1E8-1E14. The evaluated data come from an experiment with cryogenic helium in a cylindrical cell in a configuration with cell diameter D = 30 cm, height L = 30 cm and a second configuration with cell diameter D = 30 cm, height L = 15 cm. Miniature sensors recorded temperature fluctuations over time under various physical conditions and properties of helium. Using MATLAB software, the output parameters of the system (Nusselt and Reynolds numbers) and their dependence on the control parameters (Rayleigh and Prandtl numbers) were determined from the measured data. A new approach to the distribution of measured signals according to the direction of large scale circulation was used in the work, which leads to improved analysis. Reynolds numbers were evaluated using the so-called elliptic method. Furthermore, the work deals with the study of the coherent structure of the large scale circulation inside the cell.
|
|
|
Experimental study of turbulence downstream of a wire mesh
Uřičář, Filip ; Pech, Ondřej (referee) ; Lízal, František (advisor)
This bachelor's thesis is focused on the convection behind a mesh grid and consists of three parts. The first part presents current of knowledge in the generation and damping of the turbulence by the mesh grid. The second part presents experimental results of the measurement. The third part of the thesis is focused on experimental data processing and analysis. The method of hot wire anemometry was chosen for the speed measurement, namely Streamline by Dantec and for experimental purposes track had been constructed in the Laboratory of Ventilation Systems at the Faculty of Mechanical Engineering, Brno University of Technology. Based on the knowledge gained from the study of literature and the consultations, calculations and technical possibilities of the instruments used, grid measurements were performed for convection from 150 to 300 liters per minute, which was sufficient to generate turbulent flow. For the experiment, a solid grid through which the fluid flows has been chosen, due to feasibility of the experiment.
|
|
|
Wind loads of building structures
Štěrba, Martin ; Kala, Jiří (referee) ; Hradil, Petr (advisor)
The bachelor thesis deals with the analysis of the effects of wind load on building structures. In the context of the work is solved the numerical modeling of flow around the solid cylindrical bodies at high Reynolds numbers. To the simulations has been used computational software ANSYS CFX. The outputs of the work are the values of Strouhal numbers and the values of drag and lift coefficient depending on the Reynolds number.
|
|
| |
|
|
Computational Modeling of Turbulent Swirling Diffusion Flames
Vondál, Jiří ; Klemeš,, Jiří (referee) ; Tuček,, Antonín (referee) ; Hájek, Jiří (advisor)
Schopnost predikovat tepelné toky do stěn v oblasti spalování, konstrukce pecí a procesního průmyslu je velmi důležitá pro návrh těchto zařízení. Je to často klíčový požadavek pro pevnostní výpočty. Cílem této práce je proto získat kvalitní naměřená data na experimentálním zařízení a využít je pro validaci standardně využívaných modelů počítačového modelování turbulentního vířivého difúzního spalování zemního plynu. Experimentální měření bylo provedeno na vodou chlazené spalovací komoře průmyslových parametrů. Byly provedeny měření se pro dva výkony hořáku – 745 kW a 1120 kW. Z měření byla vyhodnocena data a odvozeno nastavení okrajových podmínek pro počítačovou simulaci. Některé okrajové podmínky bylo nutné získat prostřednictvím dalšího měření, nebo separátní počítačové simulace tak jako například pro emisivitu, a nebo teplotu stěny. Práce zahrnuje několik vlastnoručně vytvořených počítačových programů pro zpracování dat. Velmi dobrých výsledků bylo dosaženo při predikci tepelných toků pro nižší výkon hořáku, kde odchylky od naměřených hodnot nepřesáhly 0.2 % pro celkové odvedené teplo a 16 % pro lokální tepelný tok stěnou komory. Vyšší tepelný výkon však přinesl snížení přesnosti těchto predikcí z důvodů chybně určené turbulence. Proto se v závěru práce zaměřuje na predikce vířivého proudění za vířičem a identifikuje několik problematických míst v použitých modelech využívaných i v komerčních aplikacích.
|
|
|
Computational modeling of flow field with separation
Šamša, Petr ; Elcner, Jakub (referee) ; Jícha, Miroslav (advisor)
This diploma thesis is considering with computational modeling of flow field with separation. In the first part it contains theoretical bases of flow field computational modeling with RANS models equations and wall treatment modeling approaches included. There is also flow separation in asymmetric plane diffuser modeling described in the thesis where the most suitable turbulent model and the proper mesh parameters for the successful flow separation modeling should be chosen. Next the chosen turbulent model and parameters verification via flow separation modeling on the asymmetric 3D diffuser mesh. That analysis should ensure if the chosen turbulent model is applicable also for engineering problems. At the end of the thesis there is evaluation if the setup chosen in the thesis is suitable to apply in any practical aeroacoustics problem modeling.
|
|
|
Analysis of ventilation effect of radial channels in the rotor of electrical machines
Kratochvílová, Hana ; Marcián, Petr (referee) ; Vlach, Radek (advisor)
This thesis deals with the determination of a ventilation effect of the radial channel, that is used in a rotor of an electrical motor. CFD simulations of the channel are done in Ansys CFX software. The first chapter explains the basic theory of fans, flow, thermomechanics, CFD and structural effects of rotation on the channel. The second chapter focuses on the determination of the fan curve, the power curve, and the efficiency curve. Different types of turbulence and fluid compressibility models are used for simulations and their influence on the result is evaluated. The third part evaluates the design of the radial channel from a structural point of view.
|
|
|
Attractors in the complex dynamics of turbulent convection
Kašný, Jakub ; Nechvátal, Luděk (referee) ; Macek, Michal (advisor)
This Bachelor's thesis deals with an application of the HAVOK (Hankel Alternative View of Koopman) numerical method, which seeks attractors and predicts intermittent phenomena in dynamical systems, to data from Rayleigh-Bénard convection (RBC), which are measured at Brno Institute of Scientific Instruments in the group of Cryogenics and Superconductivity. This thesis discusses the theory on which the HAVOK is built and further deepens it compared to the article [2]. Furthermore, it enlightens some issues as the best selection of the embedding dimension r, which we selected based on the quality of regression that HAVOK creates, or the use of the Koopman operator and Taken's embedding theorem, that weren't explicitly explained in the article [2]. We discovered three different methods to compute HAVOK regressions based on and using the codes attached to the article. In the thesis, we inspect the matrices of ordinary differential equations, their behaviour when the initial values are changed and their stability for the different regression models and embedding dimensions. The solution with different initial conditions is plotted so that the attractivity can be seen. Part of the thesis contains description of RBC, its equations of motion and characteristic dimensionless numbers that describe the convection. Moreover, the thesis describes how the data are obtained and processed normally and how are processed in new ways based on the HAVOK method.
|
|
|
Library for Evaluation of Noises Used in Procedural Texturing
Kučera, Ondřej ; Chudý, Peter (referee) ; Herout, Adam (advisor)
The aim of the work is to describe procedural texturing and usage of a noise for creating textures of real materials. The reader will learn the fundamentals of the noise, its properties and a way of using it. Random numbers and interpolation methods are important parts of the noise evaluations, therefore there are chapters about random numbers generating and interpolation methods. Obviously, there is not missing the chapter, which is depicting properties and principles of several methods of creating noise. The main part of this work is effective implementation of library with a chosen noise methods, so next chapters are about choosing methods and design of the interface, implementation and many kinds of tests and optimalizations. Achieved results and final conclusions are at the end of this work.
|
guest ::
