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Flow visualization methods
Ďurdina, Lukáš ; Jedelský, Jan (referee) ; Lízal, František (advisor)
ĎURDINA, L. Flow visualization methods. Brno: Brno University of Technology, Faculty of Mechanical Engineering, 2010. 45 p. Thesis supervisor Ing. František Lízal. This thesis deals with fluid flow visualization methods with respect to their practical application possibilities. Chronological description of the historically valuable visualization experiments emphasises the role of visualization in the experimental fluid mechanics. A brief characteristic of the flow field contains mathematical description of the objects, which can be visualized. Visualization methods are divided into experimental and computer aided methods. Individual methods are ordered subsequently beginning with those with lowest requirements for equipment to the more sophisticated methods. Various techniques, which provide qualitative and quantitative description of the tested gas or liquid flow, are described. The overview for the choice of methods for various applications sums up the important facts from previous chapters. Description of a simple helium bubble flow visualization experiment realized in a lab can be found at the end of the thesis.
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Measurement of spray characteristics using optical measurement methods
Ďurdina, Lukáš ; Otáhal, Jan (referee) ; Jedelský, Jan (advisor)
Diplomová práce se zabývá měřením charakteristik sprejů dvou tlakových vířivých trysek pro spalovací komoru malého turbínového motoru na zkušebním stavu za studena pomocí metod Particle Image Velocimetry (PIV) a fázové Dopplerovské anemometrie (PDA). Cílem měření bylo stanovit a porovnat charakteristiky sprejů obou trysek. Výsledky měření mají objasnit rozdílnost chování trysek za provozu a možný dopad na proces spalování. Úvodní teoretická část pojednává o základních fyzikálních principech atomizace kapalin, konstrukci a oblasti uplatnění tlakových vířivých trysek a o principech laserových diagnostických metod použitých při experimentálním měření. Nasledující část popisuje návrh a montáž zkušební trati a dalších zařízení navržených pro experimentální měření v této práci. Experimentální část se zabývá nastavením parametrů měřícího systému a zpracováním dat. Výsledky měření zahrnují vektorová rychlostní pole, axiální rychlostní profily a distribuce velikosti kapek pro různé provozní podmínky obou trysek.
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Determination of droplet velocity and size from high-speed imaging
Juroška, Jan ; Cejpek, Ondřej (referee) ; Malý, Milan (advisor)
In this bachelor thesis there was created a method of getting velocity and size of droplets form a video using computer vision. Velocity is obtained via PIVlab toolbox in matlab, wich uses Particle Image Velocimetry. Size is obtained via matlab code. Theoretical basis on wich this code was written is included in the theoretical part of this thesis. In practical part of this thesis, accuracy of this method was evaluated and the method was applied on a video of a real spray droplet flow.
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Measurements of velocity in the channel bottom boundary layer, using Particle Image Velocimetry
Vrubel, Jan ; Haluza,, Miloslav (referee) ; Zubík, Pavel (advisor)
The theme of this thesis is continue on examining relatively commonly used measurement flow field metods, which assessing the variables flows at a high level. Thesis follow up mainly the flow field in the channel bottom boundary-layer and its depending on different factors. To calculate velocity in boundary-layer is common used extrapolation method, because this boundary layer is only the small part of measuring cross section. Increase the accuracy of measurement of flow variables make the flow in the boundary layer also important. Thesis is a summary of a basic theory of flow field, but mainly is about dependent local flow velocity on position, and about deformation of flow field in boundary layer. The aim thesis is description different calculation methods of flow flow field in boundary layer and comparison to with real condition which was measured in laboratory UVS-LVV. Real condition flow field in channel bottom boundary layer is based on exact method Particle image velocimetry. The measurement results serve to compare commonly used calculation methods or different theories velocity in the channel bottom boundary layer. Outputs this thesis offers comparison, confirmation or specification calculation methods according to the results. It has been suggested several limitations on certain methods of calculation, or coefficient were modified or alternative has been proposed to calculate them.
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Optimizing of air distribution in schools
Cigánková, Kristýna ; Šíma, Jiří (referee) ; Šikula, Ondřej (advisor)
The thesis deals with the issue of indoor air quality of schools and kindergartens. It focuses particularly on the inadequate ventilation and the application of forced ventila-tion in these types of buildings. The proposed solution is applied to a kindergarten in Kuřim. Measurements of the C02 concentration levels were performed in the presence and absence of air conditioning. To elaborate the proposed solution a simulation was made using a software called ANSYS Fluent. Input values for the simulation were obtained from an experimental measurement of a ventilation diffuser made by a company called Climecon ROX using the PIV method. This diffuser was then installed in the kindergarten. The measure-ments were carried out in the framework of the project the experimental validation of numerical models of the air flow in buildings marked with FAST-S-6-3387.
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Temporal, Spatial, and Spatio-temporal correlation of the velocity fluctuations
Jurčáková, Klára
Taylor's hypothesis about frozen turbulence [1] says that if the turbulence intensity is small compared to the mean velocity then the advection of a turbulent flow field past a fixed point can be taken entirely due to the mean flow. This means that in the “frozen turbulent field” spatial and temporal dimensions can be interchanged. Although the main assumption of Taylor's hypothesis is not met in the atmospheric boundary layer (the intensity of turbulence is usually between 10 and 20%) the hypothesis is commonly used to calculate integral length scales of turbulent fields from point measurements. Particle image velocimetry with high temporal resolution (TR-PIV) allows us to analyze both temporal and spatial cross-correlations in the turbulent flow fields and to evaluate obtained results.
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Visualization of selected flows of water and cryogenic helium using tracer particles
Pilcová, Veronika ; Skrbek, Ladislav (advisor) ; Kohout, Jaroslav (referee)
Flow visualization techniques have recently been applied for the investigation of various cryogenic flows of liquid helium. Particle image velocimetry and particle tracking velocimetry techniques, proven in the past as very fruitful in many scientific and industrial areas of research, are being used for the analysis of cryogenic flows. The Joint Low Temperature Laboratory at the Charles University in Prague is the first in Europe to employ flow visualization techniques to investigate liquid helium flows. The approach had to be optimized due to a number of technical and fundamental dificulties, i.e., the optical access to the helium bath and choice of suitable tracer particles. Water experiments at room temperature were performed to prove that the experimental apparatus is well-suited for the low-temperature experiments performed as the main part of the work. The latter focused on thermal counter flow. The results from both, room-temperature experiments and low-temperature experiments are discussed and positively compared with well-known theoretical results.
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Determination of droplet velocity and size from high-speed imaging
Juroška, Jan ; Cejpek, Ondřej (referee) ; Malý, Milan (advisor)
In this bachelor thesis there was created a method of getting velocity and size of droplets form a video using computer vision. Velocity is obtained via PIVlab toolbox in matlab, wich uses Particle Image Velocimetry. Size is obtained via matlab code. Theoretical basis on wich this code was written is included in the theoretical part of this thesis. In practical part of this thesis, accuracy of this method was evaluated and the method was applied on a video of a real spray droplet flow.
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Flow field of the valve model I
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
This report is dealing with the measurement on the valve model. The model design is based on the real steam turbine valve used for steam regulation in an inlet pipe. The main goal of this investigation was to describe the physical principles related with the non-stationarities which are related with the stability of shear layers of the flow field inside the valve.
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