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Frekvenční charakteristika generátoru anulárního syntetizovaného proudu s velkým vnitřním průměrem
Krejčí, A. Petr ; Trávníček, Zdeněk ; Tesař, Václav ; Kordík, Jozef ; Pavelka, Miroslav
An annular synthetic jet actuator of large inner/outer diameter ratio of the nozzle has been developed, and four variants were designed, manufactured, and tested. The resonance frequency was estimated theoretically, based on the mechanical energy balance, and then measured by the pneumometric method. The resultant value was found to be 40 Hz. The nozzle geometry effect on the resonance frequency and on the velocity was quantified; both effects were concluded to be surprisingly small, less than 5%.
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Formation criterion for various synthetic jets: power and frequency characteristics
Kordík, Jozef ; Trávníček, Zdeněk ; Šafařík, P.
Synthetic jets are generated by periodic alternating flows. The jet parameters are: dimension, frequency, oscillation shape and amplitude. The Reynolds number (ReH) and Strouhal number (StH) (or Stokes number SH) are used as dimensionless paramers. The experiment was performed for the Reynolds number range of ReH = 500–10000 and Strouhal number range of StH = 0.2–8.9. Flow visualization and hot-wire measurement were performed. The present results focusing on the jet formation criterion agree quite well with the available literature (the criterion ReH crit = 0.16 SH2).
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Měření přestupu tepla a frekvence oscilací s fluidickým generátorem syntetizovaného impaktního proudu
Tesař, Václav ; Trávníček, Zdeněk ; Kordík, Jozef ; Randa, Zdeněk
The paper discusses recent results of an experimental research of annular impinging hybrid-synthetic jets generated by a no-moving-part fluidic actuator. The actuator is based on a new principle and the first part of the paper discusses the basic configuration idea and the relationship with earlier hybrid-synthetic jet generators. The next part of the paper provides information of a strange phenomenon – an unexpected high-temperature region found on the impingement surface. Also discussed are the measurements of the oscillation frequency. The most important result is the substantial increase of heat transfer efficiency compared with the steady flow from the same nozzles.
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Analysis of the synthetic jet at the actuator output
Kordík, J. ; Šafařík, P. ; Vít, T. ; Trávníček, Zdeněk
The paper focuses on a pulsatile axisymmetric flow in an outlet orifice of a zero-net-mass-flux actuator of a synthetic air jet. A simplified task (pulsatile pipe flow) is studied theoretically. Velocity profiles have been measured using hot-wire anemometry; the approximation of the experimental data is based on the theoretical solution. The results improve our knowledge of synthetic jets and provide data for their advanced numerical simulation.The paper focuses on a pulsatile axisymmetric flow in an outlet orifice of a zero-net-mass-flux actuator of a synthetic air jet. A simplified task (pulsatile pipe flow) is studied theoretically. Velocity profiles have been measured using hot-wire anemometry; the approximation of the experimental data is based on the theoretical solution. The results improve our knowledge of synthetic jets and provide data for their advanced numerical simulation.
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Impinging Synthetic Jet - Experiment
Kordík, J. ; Trávníček, Zdeněk ; Šafařík, Pavel
The paper deals with processing of an experimental data relating to an impinging synthetic jet. Impinging synthetic jet means a pulsating jet, spreading onto a wall (in this case naphthalene wall). The aim of the experiment is a quantification of mass transfer on the wall and a prediction of heat transfer by means of the heat/mass transfer analogy.
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Pension Reform Issue in the light of running demograhpic developement
Kordík, Jan ; Klazar, Stanislav (advisor) ; Weberová, Jana (referee)
This Thesis discusses the pension system issues in the Czech Republic depending on a demographic situation. The first chapter affords the historic review of pension systems and shows information concerning actual applications. The second chapter is aimed at the financial variations of the pension system. The third chapter is focused on a basic description of the contemporary pension system in the Czech Republic and historic evolution as well. In the fourth chapter, there is made an excurse throught the reformed pension systems abroad. This is provided in case of post-communist countries as well as the Latin America`s country. In the fifth chapter, there is realized an appropriate analysis of financing the actual pension system in dependence on a population evolution. There is proved an indefensibility of PAYG model through the use of a mathematic model. At the begining of the closing chapter there is a conception of each political party. The second part of its is represented by own summary and conception of this "stalemate" situation.
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Udržitelnost důchodového systému ve světle probíhajících demografických změn
Kordík, Jan ; Velikovský, Jakub (advisor)
Baklářská práce se zabývá zkoumáním udržitelnosti důchodového systému v ČR v závislosti na demografickém vývoji. První kapitola podává historický přehled důchodových systémů a poskytuje informace o jejich současné aplikaci. Druhá kapitola je zaměřena na jednotlivé variace financování důchodového systému. Kapitola třetí je věnována obecnému popisu současného důchodového systému v ČR a zahraničí. V poslední kapitole je provedena patřičná analýza financování důchodového systému v závislosti na populační evoluci.
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