Browsing by Author "Primas, Jiří"

Now showing 1 - 9 of 9
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    Calculation and measurement of a neutral air flow velocity impacting a high voltage capacitor with asymmetrical electrodes
    (Amer Inst Physics, 2014) Malík, Michal; Primas, Jiří; Kopecký, Václav; Svoboda, Miroslav
    This paper deals with the effects surrounding phenomenon of a mechanical force generated on a high voltage asymmetrical capacitor (the so called Biefeld-Brown effect). A method to measure this force is described and a formula to calculate its value is also given. Based on this the authors derive a formula characterising the neutral air flow velocity impacting an asymmetrical capacitor connected to high voltage. This air flow under normal circumstances lessens the generated force. In the following part this velocity is measured using Particle Image Velocimetry measuring technique and the results of the theoretically calculated velocity and the experimentally measured value are compared. The authors found a good agreement between the results of both approaches. (C) 2014 Author(s).
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    Measurement of pulsatile flow characteristics in interaction with rigid and flexible wall
    (Technická univerzita v Liberci, ) Jašíková, Darina; Kotek, Michal; Malík, Michal; Primas, Jiří; Kopecký, Václav; Fakulta mechatroniky, informatiky a mezioborových studií
    Pulse flow was generated by a membrane pump. The nature of the pulsatile flow was measured with pressure sensors. We got information on the pressure development inside the circuit. Each phase of the pulse was evenly divided into 10 equal time slots. The individual slots were synchronized to the initial pressure change at 0.14Bar. The evaluation of the pressure measurement has already revealed the backward effect of the flexible wall. Especially when compared to glass rigid wall. Differences in pressures course are mostly significant in the peak width and lower stabilised pressure value. The flexible material absorbs part of pressure and expands its diameter. The liquid flow can be divided into four regimes: The first regime corresponds to pressure increase. The liquid flow is accelerated. The maximal fluid velocities reach 440 mm/s (Re 8800). The second regime is the highest point of pressure increase, where physically occurs the maximum membrane inclination, and closure of the pumps valves. At this point, the fluid stagnates, resulting in slowing down of the flow rate to 70 mm/s (Re 1400), and changing the characteristic velocity profile. This regime can be said as transient mode. The velocity profile is characterized with typical velocity decrease in the middle of cross section. This effect was found for both measurements – using rigid and flexible wall. The other phase of liquid acceleration can be observed in the third regime. Here, the liquid is fed with the pump. This acceleration last during the pressure decrease. This regime is characteristic with turbulent profile shape, and maximal flow velocity reach 260 mm/s (Re 5200). The fourth regime is observed since 6/5π period, when the pressure drop and starts to be stabilized. Here we can observe the liquid flow slowdown that is close to laminar profile shape. The maximal velocities in this regime are 35 mm/s (Re 700). There is an oscillation of a pressure, which leads to the formation of vortex structures near the wall. These structures are highlighted by the elasticity of the wall. The vortex structures were analysed using Proper Orthogonal Decomposition (POD). The most significant modes are for transient part of fluid flow and turbulent zone. The first 20 decomposition modes can be said as dominant. Here can be found vortex structures with kinetic energy of 10%. The nonstationary backward vortexes are developed close to the wall, as the fluid flow velocity is very small. The prevailing dominant effect on the fluid flow comes from the released kinetic energy from the relaxing flexible walls, especially in the fourth regime of pressure course. This effect is not significant for rigid walls. There were set an experimental setup for studying of cavitation base on Ventury tube. The fluid flow was analysed using high speed visualization methods in two interrogation areas in crosssection. The region of interest was focused on the swirling cavitation structure. The experiments run in 2018 were run in rigid wall. The fluid was also seeded with fluorescent particles for PIV measurement so the simple visualization was filled with fluid motion data’s. The investigated area was observed with synchronized two cameras recording parallel. The set of images were processed using supressing and dewarping algorithms. The experimental setup is prepared for the measurement on flexible wall and pulsatile flow.
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    Mixing of two immiscible phases measured by industrial electrical impedance tomography system
    (EDP SCIENCES S A, 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE, 2019) Malík, Michal; Primas, Jiří; Kotek, Michal; Jašíková, Darina; Kopecký, Václav
    The mixing of two immiscible phases is a process commonly seen in many industrial applications. Whether it is desirable (e.g. mixing of ingredients in chemical or food industry) or undesirable (e.g. sediments or contaminants in water purification) process, it has to be taken into consideration and a detailed description would be beneficial to any end product. This paper deals with a method for observing the volume ratio of two immiscible phases from the state of total separation to the state of a homogenous mixture using industrial Electrical Impedance Tomography (EIT) system ITS p2+. This paper also shows a great advantage in combining the EIT measuring method with a theoretically derived formula. It is used to calculate the concentration of a non-conductive phase in the final mixture using the initial and final conductivity values. The authors were also able to show a possibility to successfully use the formula in situations, where the initial conditions for it are not fully met.
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    Technologické teorie vzdělávání a jejich aplikace do výuky fyziky
    (Technická Univerzita v Liberci, 2011) Primas, Jiří; Horák, Josef
    This bachelor thesis deals with the application of technological theories into the processof teaching physics. The basic facts about modern theories of education with the emphasison technological theories are summed up in the background research. Next a commented listof pedagogical research methods is presented.In the main part of the thesis the pedagogical research methods are used onthe particular school to analyze the application of technological theories in the physicslessons. The results of this research are evaluated, discussed and a conclusion is drawn.
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    Vliv elektrických veličin na Biefeld-Brownův efekt
    (Technická Univerzita v Liberci, ) Primas, Jiří
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    Vliv termoemise na velikost síly při Biefeld-Brownově efektu
    (Technická Univerzita v Liberci, 2013) Kubáň, Martin; Primas, Jiří
    Cílem mojí bakalářské práce je prozkoumat, jaký vliv má termoemise na velikost síly vznikající na vysokonapěťovém kondenzátoru s asymetrickými elektrodami. Hlavně jsem se zaměřil na tenkou elektrodu, kterou jsem žhavil pomocí protékajícího proudu pomocí plovoucího zdroje proudu. V rešerši jsem shrnul poznatky a nejdůležitější pojmy. Převážně to byly druhy ionizací a typy výbojů týkající se Biefeld-Brownova efektu. V další části mojí bakalářské práce jsem vypracoval svůj úsudek o očekávaném výsledku z mého měření. Vytvořil jsem zařízení pro změnu průtoku elektrického proudu, které jsem používal pro žhavení a vyvolání termoemise tenké elektrody. Dále jsem vytvořil model, na kterém jsem mohl vytvořit pomocí vysokého napětí Biefeld-Brownův efekt. V závěru své práce jsem zhodnotil vliv termoemise na velikost vznikající síly a učinil jsem závěry v souladu s teoretickými podklady Biefeld-Brownova efektu.
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    Výzkum kmitání lopatek vodní turbíny s ohledem na poskytnutí rozšířeného pásma regulace pro zajištění stability a bezpečnosti energetické soustavy
    (2019-01-31) Kopecký, Václav; Kotek, Michal; Jašíková, Darina; Primas, Jiří; Malík, Michal; Fakulta mechatroniky, informatiky a mezioborových studií
    Na TUL byly v roce 2018 prováděny experimentální činnosti popisující chování proudění v okolí lopatky. Nadále byla rozvíjena metodika pro vyhodnocení pohybu kmitající lopatky v proudu. Činnosti navázaly na přípravné práce z roku 2017. Proudové pole v okolí lopatky bylo proměřeno metodou Time Resolved PIV. Jedná se o obdobu klasické metody PIV, kde snímkovací frekvence dosahuje řádově tisíce Hertz. Takto rychlý záznam umožňuje zachytit pohyb lopatky vybuzený proudem.
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    Zefektivnění akumulace energie a zajištění stability rozvodné sítě rozšířením provozního pásma přečerpávacích vodních elektráren
    (2019-01-31) Kotek, Michal; Jašíková, Darina; Kopecký, Václav; Primas, Jiří; Malík, Michal; Primas, Jiří; Fakulta mechatroniky, informatiky a mezioborových studií