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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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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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Characterization of Turbulent Flow in a Breakup Cell.
Vejražka, Jiří ; Zedníková, Mária ; Stanovský, Petr
Our research focuses on breakup of bubbles and drops induced by a flow turbulence. In this contribution, we describe the experimental setup used for studying the breakup, and we characterize flow within it. The setup is a rectangular glass cell, in which a turbulent flow is generated by a set of coaxial nozzles. The flow within it is characterized by means of particle image velocimetry. From the velocity data, i) local dissipation rate (ε) is estimated using Large-Eddy PIV method, and ii) statistics of velocity difference in two points is evaluated. Estimation of ε is validated by integrating the total dissipation in the setup, which reasonably agrees with the injected kinetic energy. The probability density function of velocity difference is non-Gaussian and when properly normalized, it is universal within the setup.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_C22016120713100 - PDF
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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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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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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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PIV and LIF study of slot continuous jet at low Reynolds number
Broučková, Zuzana ; Hsu, S.-S. ; Wang, A. B. ; Trávníček, Zdeněk
This study deals with a continuous jet issuing from a small narrow slot with a width of 0.36 mm. The experimental arrangement is based on the piezoelectric synthetic jet actuator studied previously for easy comparisons. The working fluid is water at room temperature. The experiments were performed using methods of particle image velocimetry (PIV) and flow visualization (laser induced fluorescence, LIF). The time-mean volume flux through the exit nozzle was quantified using precise scales. The mean velocity and the Reynolds number were evaluated as Um = 0.12 m/s and Re = 90, respectively. The results of LIF and PIV techniques revealed the three-dimensional character of the flow field, namely the saddle-shape velocity profiles. This behavior is typical for steady jets from a rectangular nozzle. The obtained results were compared with previous measurements of the synthetic jet issuing from the same cavity and the slot nozzle.
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PIV measurement of synthetic jet array
Dančová, Petra ; Vít, Tomáš ; Kotek, M.
This paper describes PIV experiments of a synthetic jet array. This part of measurements is an important step of the general study of a channel flow which is affected by synthetic jet array with emphasis on low Reynolds numbers. The study is experimental. The experiments are performed with water as the working fluids, and PIV method is used.
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