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Experimentální mechanika tekutin 2008 - sborník konference
Dančová, Petra ; Vít, Tomáš
The conference will focus on obtaining an overview of projects under investigation, and experimental methods used in the field of fluid mechanics and thermodynamics. Its aim is to organize a network of young research workers who are interested in experimental, and also theoretical, work in the field of fluid mechanics and thermodynamics. The conference should contribute to creating the closer contacts and sharing experience in application of various experimental methods, preparation and implementation of experiments, processing of results and numerical simulations of experiments. Conference proceedings are listed in ISI-Web of Knowledge
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Termoakustický prime mover – demonstrace a prvotní experimenty
Chen, Y.-Ch. ; Vít, Tomáš ; Lédl, V. ; Kordík, Jozef ; Maršík, František ; Wang, A. B. ; Doleček, R. ; Trávníček, Zdeněk
The present paper focuses on an experimental investigation of the thermoacoustic prime mover (sound generator), which was designed with the quarter-wave resonant tube. The working fluid was air under the barometric pressure. This study proves function of the prime mover, and demonstrates variety of experimental methods for experimental investigation of the thermoacoustics: acoustic measurements (the resonant frequency, power spectrum, and sound pressure level), temperature measurement (temperatures along the resonant tube, namely near the thermoacoustic stack), hot-wire measurement (oscillation velocities and displacements), and optical experiments by the holographic interferometry.
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Využití nevratné termodynamiky k popisu tekutin a pevných látek
Maršík, František
The II. Law of Thermodynamics is interpreted as an evolution law of all material systems, which are in interaction with their surroundings. The most important quantity is the entropy, which is defined by the balance law of entropy. The production of the entropy gives information about the processes into the systems and the convexity of the entropy informs us about the stability of the system states. Under the appropriate outer conditions the fluctuations can to drive the systems to an instability. This lecture is devoted to the fluid flow stability and life assessment of thermoviscoelestic solids components.
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Thermoakustic prime Mover – demonstrace a první experimenty
Chen, Y.-C. ; Vít, T. ; Lédl, Vít ; Kordík, Jozef ; Maršík, František ; Wang, A. B. ; Doleček, R. ; Trávníček, Zdeněk
The present paper focuses on an experimental investigation of the thermoacoustic prime mover (sound generator), which was designed with the quarter-wave resonant tube. The working fluid was air under the barometric pressure. This study proves function of the prime mover, and demonstrates variety of experimental methods for experimental investigation of the thermoacoustics: acoustic measurements (the resonant frequency, power spectrum, and sound pressure level), temperature measurement (temperatures along the resonant tube, namely near the thermoacoustic stack), hot-wire measurement (oscillation velocities and displacements), and optical experiments by the holographic interferometry.
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Dynamika proudění uvnitř městské křižovatky: charakteristiky šikmosti a špičatosti
Kellnerová, Radka ; Jaňour, Zbyněk
The experiment uses wind-tunnel modeling method to investigate an intermittent ventilation of pollutants within an urban intersection and adjacent canyon. The skewness and kurtosis of velocity components were obtained in order to identify an area with strong intermittent tendency. Pollutants have released from line source and mean concentration was obtained using slow flame ionization detector. Vertical vortices as well as corner vortices are responsible for accumulation of emissions emitted by vehicle traffic. However, flow instabilities corresponding to enhancement of skewness can reduce or enhance the instantaneous level of exhalations. Vertical and horizontal momentum flux was analyzed by quadrant analysis. The method has detected the localities with highest momentum transfer from free stream down to the canyon. The connection between sweep and skewness in this area was found.
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Experimentální studie o matematickém modelování velmi rychlého pneumatického systému
Hrubý, Jan ; Šmíd, Bohuslav ; Pavelka, Miroslav ; Krejčí, A. Petr
We provide some general considerations for design, mathematical modeling, and experimental testing of pneumatic systems with typical transient times of 1 ms. The gas flow is typically critical or near-critical, with significant compressibility effects. We provide a lumped model of a pneumatic system, incorporating the balances of mass, energy and momentum. We show that inertia of the gas plays an important role. For a particular system, designed for application in fundamental research of aerosol particles, we show a reasonable agreement of the lumped model with experimental test of the prototype.
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Rezonanční frekvence generátorů syntetizovaných proudů
Kordík, Jozef ; Trávníček, Zdeněk ; Šafařík, P.
This contribution focuses on axisymmetric synthetic jet actuators from the theoretical point of view. In order to evaluate their resonance frequencies, four mathematical models were derived. The results were compared with experimental data, and analyzed. With respect to the theoretical and experimental results, the applicability and limits of the models were discussed. The results illustratively prove correctness of the previous derivation based on transformation of mechanical energy.
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Laminární vírová řada za ohřívaným válcem při nerovnoměrném rozložení teploty povrchu
Trávníček, Zdeněk ; Šponiar, D.
Laminar vortex shedding (von Kármán vortex street) of a circular cylinder has been investigated under non-isothermal conditions. Numerical simulation focusing on both fluid dynamics and heat transfer has been performed, and the results were compared with experimental data. Flow was assumed to be two-dimensional, laminar, incompressible or compressible. The working fluid was air. A particular attention was given to simulate various thermal boundary conditions on the cylinder surface. The effect of the type of various thermal boundary conditions on wake flow dynamics and heat transfer was not identified in the present numerical simulations.
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