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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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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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Numerical solution of the cavitation bubble dynamics
Münster, Filip ; Himr, Daniel (referee) ; Rudolf, Pavel (advisor)
This thesis deals with the numerical solution of cavitation bubble dynamics and with cyanobacteria gas vesicle behaviour. A program for the numerical calculation of bubble dynamics is created using the Rayleigh-Plesset equation and its modifications. Subsequently, bubbles of different sizes are investigated during acoustic cavitation with various driving frequencies. Furthermore, a model for hydrodynamic cavitation is created. The model combines CFD computation of flow in the Venturi nozzle with the cavitation bubble dynamics calculation. The last part of the work is dedicated to cyanobacteria gas vesicle behaviour in a variable pressure field and during passage through the Venturi nozzle.
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Mutual interaction of magnetic field and cavitating flow
Harazin, Přemysl ; Štigler, Jaroslav (referee) ; Rudolf, Pavel (advisor)
Presented work consists of research and experimental part. Main focus of the research part is on mutual interaction between magnetic field and water and between magnetic field and cavitating flow. Prediction of the result is almost impossible, because the opinions on the effects differ, sometimes even go against each other. Experimental part consisted of three trials with permanent magnets. Electromagnetic probe was employed for measuring of the voltage. It appears, that magnetic field affects the cavitation, because in all of the trials the measured voltage changed after the switch from non-cavitating to cavitating flow. The change of the voltage was not great enough, thus application of this phenomenon in practice cannot be recommended.
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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.
|
|
|
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.
|
|
|
Numerical solution of the cavitation bubble dynamics
Münster, Filip ; Himr, Daniel (referee) ; Rudolf, Pavel (advisor)
This thesis deals with the numerical solution of cavitation bubble dynamics and with cyanobacteria gas vesicle behaviour. A program for the numerical calculation of bubble dynamics is created using the Rayleigh-Plesset equation and its modifications. Subsequently, bubbles of different sizes are investigated during acoustic cavitation with various driving frequencies. Furthermore, a model for hydrodynamic cavitation is created. The model combines CFD computation of flow in the Venturi nozzle with the cavitation bubble dynamics calculation. The last part of the work is dedicated to cyanobacteria gas vesicle behaviour in a variable pressure field and during passage through the Venturi nozzle.
|
|
|
Mutual interaction of magnetic field and cavitating flow
Harazin, Přemysl ; Štigler, Jaroslav (referee) ; Rudolf, Pavel (advisor)
Presented work consists of research and experimental part. Main focus of the research part is on mutual interaction between magnetic field and water and between magnetic field and cavitating flow. Prediction of the result is almost impossible, because the opinions on the effects differ, sometimes even go against each other. Experimental part consisted of three trials with permanent magnets. Electromagnetic probe was employed for measuring of the voltage. It appears, that magnetic field affects the cavitation, because in all of the trials the measured voltage changed after the switch from non-cavitating to cavitating flow. The change of the voltage was not great enough, thus application of this phenomenon in practice cannot be recommended.
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