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Cavitation testing using cavitating jet
Rovder, Juraj ; Dobšáková, Lenka (referee) ; Rudolf, Pavel (advisor)
This thesis deals with the issue of cavitation and its effects. In this context, it describes the mechanism of origin and implosion of cavities and cavitation regimes. It lists various types of hydrodynamic cavitation. It presents the Rayleight-Plesset equation and describes micro jet. It also highlights cavitation erosion and the effects of cavitation on some types of materials. It deals with three types of cavitation resistance testing, namely cavitation tunnels, a vibrating cavitation system, supported by the ASTM G32 standard, and last but not least, cavitation nozzles, which follow the ASTM G134-17 standard. In correlation with cavitation nozzles, it frames its four basic parameters, which are stand of distance, the cavitation number, the speed of sound and the geometry of the nozzle. At the end of the theoretical part it characterizes the construction of test bench. The practical part is focused on performing the experiment. It first presents the procedure for carrying out the experiment and then evaluates this experiment. Part of the evaluation is the visual observation of selected samples of AlCu4Mg1Mn1 material and the monitoring of cavitation erosion on specific samples. First, these data are processed in the form of graphs and tables. It uses a microscope as a tool for detailed observation of samples. The conclusion of the practical part is devoted to the evaluation of the experiment.
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Mathematical Model of Vehicle Damper
Vrba, Michal ; Hejtmánek, Petr (referee) ; Blaťák, Ondřej (advisor)
This master’s thesis describes development of parametric model of monotube damper which would be able to predict damping forces. This model is intended for 3-way racing dampers which are built with foot valve and external adjusters. Each flowing path was included to calculate the damping force. Also, mathematical model for shim stiffness was created. First part of the master’s thesis was focused on the description of function of the damper and physical effects that influence damping characteristic. In the next part, the mathematical model was described. The damper was correlated and validated on damper dynamometer. Final part of thesis focuses on the investigation of input arguments and their influence on resulting damping.
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Cavitation erosion
Lecnar, Lukáš ; Hudec, Martin (referee) ; Rudolf, Pavel (advisor)
This bachelor’s thesis focuses on cavitation erosion and it is divided into two main parts. The first part is devoted to the search of cavitation erosion focusing on erosion mechanisms. In the first chapter of this search is briefly described cavitation process and different types of cavitation are listed here. Hydrodynamic cavitation which is the key type for this bachelor’s thesis is described in the following chapter. The final and the most extensive chapter is devoted to cavitation erosion of solids which is largely associated with the effects of the mechanical action of the fluid. The second part is devoted to the experimental study of cavitation erosion of samples. The goal was to document the experiment which was carried out in order to gain knowledge about the material removal by cavitation erosion.
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Cavitation assessment from flow rate drop and high-frequency pressure pulsations.
Šebek, Miloš ; Hudec, Martin (referee) ; Habán, Vladimír (advisor)
Main issue of this master´s thesis deals with high-frequency pulsations caused by cavitating hydraulic components (in this case nozzle and throttle valve). In first measurement on the nozzle was not a high-frequency sensor set in the way, so the evaluation was incorrect. After re-setting of the way was the nozzle measured again and the pulsations were evaluated correct this time. During the last measurement was the sensor located behind the throttle valve, which was with gradual opening and cavitation treatment measured. Resulting dependencies worked out on time dependence. A special mathematical method, Fourier transformation, was used. It transformed pressure amplitudes into frequency dependence. Evaluation of dependecies is the basic step for frequency band assesment, in which the cavitation on particular components happens.
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Lagrangian tracking of the cavitation bubble
Bossio Castro, Alvaro Manuel ; Zatočilová, Jitka (referee) ; Rudolf, Pavel (advisor)
In this thesis, the dynamics of an isolated cavitation bubble submerged in a steady flow is studied numerically. A Lagrangian-Eulerian approach is considered, in which properties of the fluid are computed first by means of Eulerian methods (in this study the commercial CFD software Ansys Fluent 19 was used) and the trajectory of the bubble is then computed in a Lagrangian fashion, i.e. the bubble is considered as a small particle moving relative to the fluid, due to the effect of several forces depending on fluid's pressure field, fluid's velocity field and bubble's radius. Bubble's radius dynamics, modeled by Rayleigh-Plesset equation, has a big influence on its kinetics, so a special attention is given to it. Two study cases are considered. The first one, motivated by acoustic cavitation is concerned with the response of the bubble's radius in a static flow under the influence of an oscillatory pressure field, the second one studies the trajectory of the bubble submerged in a fluid passing by a Venturi tube and a sharp-edged orifice plate.
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Cavitation in engineering praktice
Kianička, Martin ; Hudec, Martin (referee) ; Pochylý, František (advisor)
This diploma thesis contains three parts. The first part is a background research which deals with notions such as cavitation and cyanobacteria. It also contains current phase in the use of cavitation. The second part deals with design, composition and constructional solution of hydraulic circuit on the riverboat. The third part deals with experimental certification of the cavitation effect on the cyanobacteria in the water. Design of the riverboat with the hydraulic circuit including the circuit itself and the cavitation tube was created in SolidWorks program, calculations, it’s processing and graphs were created in Microsoft Excel.
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Contradictions analysis of small water power Ostravice.
Kupčík, Roman ; Skoták, Aleš (referee) ; Haluza, Miloslav (advisor)
The main subject of the diploma thesis „Contradiction analysis of small water power Ostravice“ is solution of reduced output of small water power plant on the river Ostravice near the town Vratimov. Power plant equippment is axial flow Kaplans turbine RA – 3,5 – 0 1000 with runner diametr 1000 mm. Low output is caused by draft tube. New draft tube is designed in this masters thesis. For hydraulic layout was used CFD software Fluent. The aim of this work is finding of optimal shape which leads to increasing of power from current 30 kW to projected 55 kW.
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Nano and microbubbles created by cavitation
Harazin, Přemysl ; Sluše, Jan (referee) ; Rudolf, Pavel (advisor)
This work solves the problematics of distinguishing tiny bubbles and particles as well as the thermodynamics of bubbles and their creation. The process of cavitation is described in the first part of the thesis. The problem of visualisation and counting the number of bubbles is described in the experimental part as well as the posibility of influencing the stream through the input of obstacles. Problem with visualisation was dealt with laser beam shining through the transparent tube with software postprocessing. The issue of influencing the stream was dealt with input of the strainer into the stream. Results of these experiments are, that with good ambient light situation, the laser beam ensures good visualisation of bubbles and particles and therefore the posibility of counting the number of bubbles with the help of a software. The usage of strainer helped to create bigger number of tiny bubbles.
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