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Time progression of metrological characteristics of electromagnetic current meters
Březina, Jiří ; Brázda, Martin (referee) ; Žoužela, Michal (advisor)
This experimental diploma thesis investigates the changes in the metrological characteristics of the electromagnetic current meter of velocity. The theoretical part of the thesis includes a brief summary of technical and metrological characteristics of these types of devices. In addition, it describes the tested device, the test track, and the measurement procedure, which consists of two variants: long-term monitoring with a relatively regular monthly measurement interval and short-term monitoring with a regular daily measurement interval. The evaluation of the experimental work focuses on the repeatability and variability of the displayed point speed values and their stability over time. Furthermore, the parameters reported by the meter during long-term and short-term monitoring are compared to each other. The results are also compared with similar experiments.
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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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Evaluation Of Uncertainties Of River Flow Measurements With Propeller Current-Meter
Niemiec, Łukasz ; Macura,, Viliam (referee) ; Kožnárek, Zdeněk (referee) ; Starý, Miloš (advisor)
The development of hydrology and the need of getting exact data increase the demands on hydro metering. Measurement of spot velocities and deriving the flow of water are frequently performed by the workers of Český hydrometeorologický ústav (Czech Hydrometeorological Institute) and other companies. The limited precision of the measuring machines, the imperfection of methods and the influence of human senses cause that we are not able to get the accurate value of quantity. We are just close to the right values. The term uncertainty of measuring determines the interval which is assigned to each measurement and contains the real value of measured quantity. Twenty imminently repeated measurement were done in twelve measuring profiles of the Dyje River and in one profile of the Morava River using the current meters OTT (OTT Hydromet, 2013) type C2 and type C31. We investigated the dependence of uncertainties type A and B in different profile parameter. The measurement was done with the suspension bar with 2 to 4 propeller current-meters. The hydrometric car on the bridge was used in deeper waters. The results were analysed from the point of view of the uncertainties and generalized. Next point of the research was to find out how the frequency of the current meter depends on temperature of water. For this purpose, the specific canal was made in the Faculty of Civil Engineering in Brno (Ústav vodního hospodářství krajiny) and the measuring was done in temperature interval from 1 °C to 24 °C. Repeated measuring was statistically evaluated from the uncertainties point of view. In the thesis, the proposal of elaboration of uncertainties determined by both types of measurement into current methods of determination of uncertainties of the derived flows using the measurement of spot velocity by the propeller current-meter in measuring profiles of the rivers is introduced.
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Change of bed roughness by particle separation in the surface layer
Roháčová, Denisa ; Šedivý, Jiří (referee) ; Zachoval, Zbyněk (advisor)
This master thesis is divided into two parts: theoretical and practical one. In the theoretical part there is described hydraulic roughness, velocity distribution in the case of hydraulically rough surface and the process of grain sorting in surface layer. The practical part of the thesis resolves the influence of surface layer on hydraulic roughness of bed, expressed by Nikuradse sand grain size ks. The results are formulas explaining dependence of ks on characteristic grain size dx from grain-size distribution curve and comparison with coefficient ks according to different authors.
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Electromagnetic current meters of velocity
Březina, Jiří ; Zubík, Pavel (referee) ; Žoužela, Michal (advisor)
This bachelor thesis explains the issue of electromagnetic current meter of velocity. A survey of all available standards on these devices is carried out. Devices are described technically and metrologically. There are also described the possibilities of usage, operating conditions as well as problems of calibration of these devices. Information on available commercially available devices is provided along with a description of all relevant parameters. One selected device model is put to the test of measurement the velocity on the calibration tank of the laboratory, thus the experiences from real calibration measurement are gained and described.
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Metrological characteristics of current velocity meters using the electromagnetic principle of measurement
Vítů, Martin ; Brázda, Martin (referee) ; Žoužela, Michal (advisor)
This master’s thesis deals with the assesment of directional sensivity and accuracy of current stream velocity using electromagnetic induction meters in circumstances simulating the real measurement profiles condictions. The theoretical part of the thesis describes the issue of streamflow measurement in open channels and determination of the relevant measurement uncertainties. It also includes description of the hydraulic circuit and the subject current velocity meters. The experimental part of the thesis focuses on the effect of turbulence on the value and accuracy of measured velocity and directional sensivity of electromagnetic induction meters of current velocity. The results are compared with parameters given by manufacturers, research by other authors and with the metrological characteristics of hydrometric propellers, which are commonly used for streamflow measurement in open channels.
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Metrological characteristics of current velocity meters using the electromagnetic principle of measurement
Vítů, Martin ; Brázda, Martin (referee) ; Žoužela, Michal (advisor)
This master’s thesis deals with the assesment of directional sensivity and accuracy of current stream velocity using electromagnetic induction meters in circumstances simulating the real measurement profiles condictions. The theoretical part of the thesis describes the issue of streamflow measurement in open channels and determination of the relevant measurement uncertainties. It also includes description of the hydraulic circuit and the subject current velocity meters. The experimental part of the thesis focuses on the effect of turbulence on the value and accuracy of measured velocity and directional sensivity of electromagnetic induction meters of current velocity. The results are compared with parameters given by manufacturers, research by other authors and with the metrological characteristics of hydrometric propellers, which are commonly used for streamflow measurement in open channels.
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Time progression of metrological characteristics of electromagnetic current meters
Březina, Jiří ; Brázda, Martin (referee) ; Žoužela, Michal (advisor)
This experimental diploma thesis investigates the changes in the metrological characteristics of the electromagnetic current meter of velocity. The theoretical part of the thesis includes a brief summary of technical and metrological characteristics of these types of devices. In addition, it describes the tested device, the test track, and the measurement procedure, which consists of two variants: long-term monitoring with a relatively regular monthly measurement interval and short-term monitoring with a regular daily measurement interval. The evaluation of the experimental work focuses on the repeatability and variability of the displayed point speed values and their stability over time. Furthermore, the parameters reported by the meter during long-term and short-term monitoring are compared to each other. The results are also compared with similar experiments.
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Electromagnetic current meters of velocity
Březina, Jiří ; Zubík, Pavel (referee) ; Žoužela, Michal (advisor)
This bachelor thesis explains the issue of electromagnetic current meter of velocity. A survey of all available standards on these devices is carried out. Devices are described technically and metrologically. There are also described the possibilities of usage, operating conditions as well as problems of calibration of these devices. Information on available commercially available devices is provided along with a description of all relevant parameters. One selected device model is put to the test of measurement the velocity on the calibration tank of the laboratory, thus the experiences from real calibration measurement are gained and described.
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