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Study of the Dissipation in Spiraling Vortical Structures
Štefan, David ; Drábková, Sylva (referee) ; Koutník,, Jiří (referee) ; Skoták, Aleš (referee) ; Rudolf, Pavel (advisor)
This work deals with study of swirling flows where the spiral vortical structure appears. The main relation is to flow seen in the draft tube cone of hydraulic turbines operated out of the design point (i.e. best efficiency point). In this cases large coherent vortex structure (vortex rope) appears and consequently high pressure pulsations are propagated to the whole machine system leading to possible restriction of turbine operation. This flow features are consequence of flow instability called vortex breakdown in case of Francis turbine operated at part load (flow rate lower than optimal one). The present study is carried out using simplified device of swirl generator in order to access similar flow conditions as can be found in real hydraulic turbines. Both the dynamic and dissipation effect of spiral vortex breakdown are investigated. The first part of thesis deals with spiral form of vortex breakdown. The experimentally measured velocity profiles (LDA) and wall static pressures are correlated with numerical simulations carried out using open-source CFD package OpenFOAM 2.2.2. The high speed camera recording of cavitating vortex core is used to obtain image ensemble for further post-processing. The dissipation effect of spiral vortex structure is in detail discussed based on computed flow fields. The second part of thesis is dedicated to the application of POD decomposition to the study of spatio-temporal features of spiral vortex dynamics. Firstly the POD is applied to the both the experimentally obtained image ensemble of cavitating vortex and numerically computed static pressure fields. Secondly the comprehensive analysis of spiral vortex mitigation effect by the axial water jet is analyzed. The collaborative study employing the swirl generator apparatus designed by the researchers from Politehnica University of Timisoara in Romania is performed and changes in spatio-temporal vortex dynamic are studied. In this study the numerical data (in a form of three-dimensional pressure and velocity fields) are obtained using commercial CFD software ANSYS Fluent R14.
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The proposal of the diagram of a pump series
Šály, Peter ; Veselý, Jindřich (referee) ; Haluza, Miloslav (advisor)
My diploma thesis describes a procedure of creating interactive computer software for company ISH&MSA Čerpadla a.s. in its theoretical part as well as in its practical part. It is a proposal diagram of centrifugal pumps which consists of made and nonmade pumps. After the selection of a certain pump, according to the required parameters of capacity of pump and transit height, the output of the programme is drawing of a flows characteristic, characteristics of coiled paddlewheel and curves of dissipation without any differences in whether the pump is made or not. There is an operating procedure from the initial work with data, short demonstrations from source code, computation of nonmeasured pump to the ascending flows characteristics in practical part of my diploma thesis. In theoretical part, there are explained principles that are needed for comprehension of a pump reform which are used in practical part.
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Influence of transverse bottom elements on energy dissipation in the stilling basin
Knoflíček, Jakub ; Haluza,, Miloslav (referee) ; Šulc, Jan (advisor)
The thesis is dealing with comparing of the kinetic energy flow dissipation in stilling basins of different cross-section, supplemented by cross bottom elements based on model research. Purpose of work is the desire to reconstruct the existing building security structure of waterworks along with increasing their capacity. Within experimental research were measured depths in different variants. Based on the results of model tests are evaluated and tabulated sorted variants of the combat effectiveness of the kinetic energy flow. The results will be used for the efficient design of additional alterations of stilling basins.
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The influence of the hub on discharge and efficiency of the swirl turbine
Husák, Martin ; Koutný, Luděk (referee) ; Haluza, Miloslav (advisor)
The aim is to determine by numerical modeling the influence of the hub on discharge and efficiency of the swirl turbine. The first part summarizes the theoretical knowledge about water turbines. In the main part is done hydraulic design of turbine, create model in Inventor, export geometry in Gambit and build mesh. Then it is described the solution methodology in Fluent, evaluation of computed data and their presentation in the form of tables and graphs
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efficiency of the bottom elements on the supercritical flow energy dissipation
Knoflíček, Jakub ; Haluza,, Miloslav (referee) ; Šulc, Jan (advisor)
The thesis is dealing with comparing dissipation of the kinetic energy water flow using various bottom elements based on model research. There is missing information about efficiency of different kinds of bottom elements. This absence does not allow to compare different modification of the bottom of stilling basins. Within experimental research were measured depths in different variants. Based on the results of model tests are evaluated and tabulated sorted variants of the combat efficiency of the kinetic energy water flow. The results will be used for the efficient and economic design of additional alterations of stilling basins.
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Study of the vortex impeller pump design
Červinka, Martin ; Koutný, Luděk (referee) ; Klas, Roman (advisor)
Diploma thesis deals with problems of design a sludge pump with a vortex impeller. Clearly summarizes the basic information on hydrodynamic pumps with a significant focus on sludge pumps. It contains a design of a vortex impeller, which is supported by CFD (Computational Fluid Dynamic) calculation in software Fluent. The aim of the work is to design vortex impeller, which could replace the existing channel impeller while maintaining the operating parameters of the pump.
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Anelastic deformation of planetary bodies
Vach, Dominik ; Čadek, Ondřej (advisor) ; Běhounková, Marie (referee)
Observations indicate an existence of subsurface oceans for some of the icy moons in the Solar System which are heated by the tidal forces. In order to describe this anelastic deformation, the methods well-known from the continuum mechanics were employed, and thus the dissipation was calculated for various bodies. In the thesis, Maxwell and Kelvin-Voigt model were compared in their ability to predict the heating power of the bodies. In contrast to the Maxwell model, the Kelvin-Voigt model, which is generally not used in geophysics, repre- sents reversible processes, and thus could explain the effects which are otherwise explained only by the gravity. A program in Fortran was developed in order to compare the models by modelling 3D anelastic deformation of planetary bodies under the effect of tidal forces. The results indicate the predicted power can be various for both models and Kelvin-Voigt model could be used e.g. to describe short run deformation processes. 1
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Anelastic deformation of planetary bodies
Vach, Dominik ; Čadek, Ondřej (advisor) ; Běhounková, Marie (referee)
Observations indicate an existence of subsurface oceans for some of the icy moons in the Solar System which are heated by the tidal forces. In order to describe this anelastic deformation, the methods well-known from the continuum mechanics were employed, and thus the dissipation was calculated for various bodies. In the thesis, Maxwell and Kelvin-Voigt model were compared in their ability to predict the heating power of the bodies. In contrast to the Maxwell model, the Kelvin-Voigt model, which is generally not used in geophysics, repre- sents reversible processes, and thus could explain the effects which are otherwise explained only by the gravity. A program in Fortran was developed in order to compare the models by modelling 3D anelastic deformation of planetary bodies under the effect of tidal forces. The results indicate the predicted power can be various for both models and Kelvin-Voigt model could be used e.g. to describe short run deformation processes. 1
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Flow of a subsurface ocean in shallow water approximation
Šafin, Jakub ; Čadek, Ondřej (advisor) ; Velímský, Jakub (referee)
In this thesis, we deal with the flow of a subsurface ocean in the so-called shallow water approximation. From the equations describing general flow of an incompressible fluid, we obtain simplified equations, applicable to a shallow global ocean on a rotating sphere. Based on these equations, we develop a program that can be used to model the flow of an ocean in 2D. We create short simulations of the flow on two icy moons, Europa and Enceladus, forced by the eccentricity and obliquity tidal potentials. The existence of subsurface oceans has been demonstrated on icy moons of outer planets; the mechanism which keeps them from freezing has remained unclear until now. Based on the flow simulations, we attempt to estimate the energy dissipation due to bottom friction. Powered by TCPDF (www.tcpdf.org)
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Monitoring of settlement of embankment subsoil
Karlín, Petr ; Novotný, Jan (advisor) ; Kudrna, Zdeněk (referee)
: During each transport buildings are used embankments, therefore it is important to carry out a detailed geological survey. The task of the survey is to determine the soil properties (soil) for such embankments, bridges and other objects depend on the load. For many objects is undesirable reduction embankment over time, this phenomenon is mainly caused by the consolidation of underlying layers. Parameters find out from the engineering-geological survey is calculating for better prediction of settlement which is based on the value of consolidation. In the following monitoring is measured by change in soil elevation relative to a reference point. These values are further processed and compared with the calculation. Main aim of this work is to unify the addiction values of loading, settlement and time for 90% consolidation.
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