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Comparison of Pulsating Flow of Newtonian and non-Newtonian Fluid in Complex Geometry
Kohút, Jiří ; Rudolf, Pavel (referee) ; Jagoš, Jiří (advisor)
This master's thesis deals with pulsating flow of Newtonian and non-Newtonian fluid. Theoretical part represents necessary theoretical knowledge for pulsating flow and understanding of non-Newtonian behaviour. Furthermore the thesis focus is directed on numerical simulation of pulsating flow in straight, ideally rigid tube and in patient-specific model of human artery, more precisely in carotid. Two methods are used: numerical solution based on finite volume method (FVM) and also analytical solution using Bessel functions by Womersley. Results are validated against experimental measurements of velocity profiles by particle image velocity method (PIV). The agreement between numerical and experimental data with consideration of PIV inaccuracy was was very good from both point of views - qualitative and quantitative. Numerical solution also compare influence of turbulence and non-Newtonian behaviour towards base (laminar flow, Newtonian fluid). Developed methodology is then applied on patient-specific model of carotid, which was renovated from computed tomography. Measurements in vivo in human arteries is very expensive and often invasive. Because of that measurement outputs are limited, most of the time on pressure and flow. Computational fluid dynamics (CFD) is non-invasive and outputs are through whole domain. Due to these advantages CFD significantly contributes to understanding of hemodynamics influence in cardiovascular diseases.
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Measuring of Velocity Profiles in Liquids by Using of UVP
Kárník, Jan ; Stejskal, Jiří (referee) ; Štigler, Jaroslav (advisor)
The following bachelor's thesis deals with one possible way of determination velocity profiles in liquids. Content of the thesis is focused mainly on the method of the UVP (Ultrasound Velocity Profile), on the ways and principles of measuring, on its pluses and cons and it´s comparison with the other conventional methods, like for the example the PIV (Particle Image Velocimetry) and LDA (Laser Doppler Anemometry). There is also the possible placement of the transducers to the measuring system discussed. Furthermore the thesis deals with trouble in the test measurement. At the beginning this work deals with familiarization with principle and function of the measuring device and with the device for the method UVP itself. Apart from the UVP measuring method the thesis also deals with short description of the competitive methods – PIV, LDA, which are used to measure the velocity profiles nowadays. Particular attention is given to the PIV method, which significance is currently growing. In conclusion, there is comparison of different methods with the UVP method made and there are the future steps to realize the successful measurement with UVP method also discussed.
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Studies on Non-Newtonian Behavior in Slit-flow rheometer at Unsteady flow
Halama, Lukáš ; Vimmr, Jan (referee) ; Roupec, Jakub (advisor)
The thesis deals with the description of the unstable flow of non-Newtonian fluid in a slit-flow rheometer, which negatively affects its behaviour. The initiators of unstable fluid flow are the roughness of the rheometer slit walls, the slip on the rheometer walls, and the influence of the inlet and outlet region geometry of the rheometer slit. The work contains methodical procedures for mathematical consideration of individual unstable fluid flow initiators and design of change of slit geometry of slit-flow rheometer. Part of the work is also a comparison of the most commonly used rheological models, derivation of general relations for the creation of the velocity profile of individual rheological models and their subsequent implementation in the rheological application, which significantly simplifies the process of evaluation of measured data when measured on slit-flow rheometer. This application can be used to determine basic parameters in CFD simulations or as a teaching aid.
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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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Simplified computer models of elements for an air distribution
Mishuk, Aliaksandra ; Gebauer, Günter (referee) ; Šikula, Ondřej (advisor)
The goal of this master thesis is to create a simplified model of an actual swirl diffuser using CFD (Computational Fluid Dynamics) simulation, so that it would be easy to calculate (would have a simple geometry, a proper mesh and would enable quick definition of the model’s boundary conditions) and would also create an airflow pattern in space as close to reality as possible. In the process a CFD model with a certain geometry was created. Subsequently, various model settings were tested. Calculation results were compared with the results of the experimental measurement done using the PIV method.
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The Fluid Flow Between Two Paralel Plates, the Comparison Between the Measruring and The Analytical Solution.
Kárník, Jan ; Hudec, Martin (referee) ; Štigler, Jaroslav (advisor)
This master's thesis is focused on measurement of the velocity profiles in liquids using ultrasound. The thesis describes two executed measurements both in the channel with free surface, both in the square shaped pipe. In the introductory part this work deals with clarifying the theoretical fundamentals associated with the measurement method UVP such as the Doppler effect, the speed of sound in the medium or the acoustic impedance of the environment. The next part describes the execution of the velocity profile measurement in the channel with free surface described and there is also the description of the results achieved during this measurement. In the last part the thesis deals with the measurement of the velocity profile in the square shaped pipe. There is also the comparison between the measured velocity profiles and the velocity profiles calculated using the analytical formula. In the conclusion there is the evaluation of achieved results.
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The limits of movement and quantification of bedload amount for gravel-bed rivers
Roušar, Ladislav ; Matoušek, Václav (referee) ; Tůma, Antonín (referee) ; Veselý, Jaroslav (advisor)
Doctoral thesis in detail and comprehensively deals with mechanic of incipient bedload motion for gravel-bed rivers. This study based on theoretical knowledge, experimental researches, numerical models and field survey extends present knowledge concerning with incipient bedload motion and sediment transport at small relative height and hydraulically rough surface bed for turbulent unaerated free surface flow. Incipient bedload motion and sediment transport have been determined for homogeneous and inhomogeneous bed materials. For homogeneous bed material the velocity profiles have been described by different methods in near the bed. Further, hydraulic flow resistance has been evaluated. In the case of inhomogeneous bed material, static armouring and influence of surface layer sorting on hydraulic roughness have been investigated. The correctness of obtained knowledge has been confirmed on the object of nature-inspired river widening. Results shown, among others, that incipient bedload motion does not depend on relative height or final armouring of surface layer to what extend hydraulic roughness is influenced.
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Hydraulic losses during unsteady flow of liquid in a pipe
Svoboda, Jakub ; Pochylý, František (referee) ; Habán, Vladimír (advisor)
This thesis is focused on solving hydraulic losses during unsteady flow of liquid in pipe for both laminar and turbulent flow in smooth pipes. Radial viscosity distribution is assumed to be the same as for steady flow. Viscosity distribution is derived from velocity profile, which is mathematically described with suitably chosen function. Laplace images of unsteady velocity profile and mean velocity in cross-section are derived depending on pressure difference. Loss coefficient is derived and on base of transfer matrix method, self-numbers are calculated. Self-numbers represent attenuation and own frequency. Self-numbers are compared to values from software called “F-ACHAR” and loss coefficient is compared to the one for quasi-steady method.
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Design and verification of lab-scale spray column for CO2 capture
Veselý, Filip ; Bělka, Miloslav (referee) ; Malý, Milan (advisor)
The concept and design of the lab-scaled spray column for CO2 capture which is capable of using optical measurement technologies and provides variations of experimental conditions is crucial to research CO2 absorption using sprays. This thesis is focused on the design of the column and all necessary components. Furthermore, there are discussed experimental conditions and measurement technologies. It provides deep look at velocity profile adjustments and efficiency of the absorption for MEA and aqueous ammonia. There is a discussion about each configuration and its results including design adjustments suggestions.
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