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Dynamika syntetizovaného paprsku
Uruba, Václav ; Knob, Martin ; Popelka, Lukáš
The paper presents recent results obtained in synthetic jet research in IT, Fluid Dynamics Department. The case in quiescent air is examined experimentally using time-resolved PIV method. Results concerning a synthetic jet mean characteristics and dynamics behaviour are presented.
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Nové metody záznamu chování volného proudu plazmatu užívající vláknovou optiku
Šonský, Jiří ; Hlína, Jan ; Něnička, Václav
The fibre optics coupling to photodiodes used in plasma jets optical radiation recording enables us to increase the channel count and to add flexibility to an experimental layout for multi-directional observations. These improvements give us opportunity of more detailed and important plasma jets behaviour analysis - reconstruction of luminosity fields (close to relative value of enthalpy) in planes perpendicular to a plasma jet axis, velocities and tracking of plasma jet axis movements. Details of experimental hardware and layount will be also shortly presented.
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Porovnání kritérií pro určení zkráceného přechodu
Příhoda, Jaromír ; Popelka, Lukáš
Empirical relations for the bypass transition were compared with experimental data and with numerical results obtained by the Xfoil code for the flat-plate flow. Relations for the transition onset and the length of the transitional region were tested for the effect free-stream turbulence. The effect of wall roughness was considered as well.
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Reference Film Temperature in the Hot-wire Anemometry
Antoš, Pavel
Dimensionless parameters in the cooling law are referred to the reference film temperature. In case of the mean film temperature there is necessary to use a temperature loading factor. There were found such reference temperatures that the loading factor is eliminated.
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Nestacionární charakteristiky impaktního proudění do korýtkové kavity
Knob, Martin ; Antoš, Pavel ; Adamec, J.
In this contribution, the unsteady behaviour of a jet, impinging into a trough cavity is described. The mechanism of the switching of the jet is clarified and the effect of the impingement angle is discussed. The problem was studied both experimentally and numerically. The numerical investigation is performed using a commercial package Fluent 6.1, while the experimental data are obtained using the hot- wire probe. The experimental and the numerical data are compared and discussed.
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Měření proudění v městském baldachýnu
Šeděnková, Hana ; Jaňour, Zbyněk
The aim of the experiment was a measurement of the flow in the urban canopy layer - the portion of boundary layer of atmosphere between the roof tops and the ground.The work took place in thwe boundary layer wind tunnel. The Laser Doppler Anemometry was used as a flow measurement technique. The simplifed model of the urban build-up area (regularly placed cubes on the ground) was put into the tunnel. The big influence of the model on the flow was found.
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Wind tunnel concentration field study in a urban area
Jaňour, Zbyněk ; Kellnerová, Radka ; Bezpalcová, Klára
The aim of the project was to study the influence of boundary conditions on contaminant spreading in a urban area model. The experiment was conducted a low-speed open-circuit tunnel. The urban area model was scaled down to 1:200. The model aimed to simulate a typical street with intense traffic, in our case specifically the Podbielski Strasse in Hannover (Germany). The downstreet flow was at an aproximate angle of 45 degrees to the street axis. Traffic was simulated by a double-line source. In the course of the experiment we have replaced a convoluted model of a park in the upstream area with simpler elements of varying size and density. We then compared the concentration field of the new arrangement with the original concentration field. All configurations led to a decrease of concentration . In ares where the original concentration had reached the highest values, the most significant decrease was obtained.
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