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Holographic interferometry as a tool for visualization of temperature fields in fluids
Dančová, Petra ; Vít, Tomáš ; Lédl, V. ; Trávníček, Zdeněk ; Doleček, R.
Measurement of temperature field in moving fluids is connected with many difficulties. Usage of point temperature measurement methods, such as Constant Current Anemometry (CCA), is limited to frequencies up to 3kHz. This frequency should be the limiting factor for using the CCA in fluid when fast change of temperature occurs. This shortcoming of CCA measurements should be overcome by using of optical methods such as digital holographic interferometry. It is necessary to employ a special holographic setup with double sensitivity instead of the commonly used Mach-Zehnder type of holographic interferometer in order to attain the parameters sufficient for the studied case. This setup is not light efficient like the Mach-Zehnder type but has double sensitivity. The special technique of acquiring and phase averaging of results from holographic interferometry is presented.
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Numerical simulations of turbulent flow through DCA 8% cascade
Trefilík, Jiří ; Kozel, K. ; Příhoda, Jaromír
The work deals with further development of numerical methods for simulation of transonic turbulent flows through the DCA 8% cascade. Results of numerical experiments modelling the viscous and inviscid flows in a cascade with various inlet Mach numbers are compared and discussed. For turbulence modelling the algebraic Baldwin-Lomax model and two- equation standard k-ω and TNT k-omega models were employed.
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Numerical experiments for turbulent flows
Trefilík, Jiří ; Kozel, Karel ; Příhoda, J.
The aim of the work is to explorethe possibilities of modelling transonic flowsin the internal and external aerodynamics. Several konfigurationswere analyzed and calculations were performed using both inviscid and viscous models of flow. Viscous turbulent flows have been simulated using either zero equation algebraic Baldwin-Lomax model and two equation k - w model in its basic version and improved TNT variant. The numerical solution was obtained using Lax-Wendroff scheme in the MAcCormack from on structured non-ortogonal grids. Artificial dissipation was added to improve the numerical stability. Achieved results are compared with experimental data.
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Visualization of the flow around rotating cylinder
Broučková, Z. ; Trávníček, Zdeněk ; Šafařík, P.
The visualization of the flow around a rotating and standing cylinder has been performed in air. This visualization has been performed for two velocities of a freestream for Reynolds numbers Re = 920 a 990 and for four frequencies of the rotation (0 s-1, 5 s-1, 12.5 s-1 and 20 s-1). The results have been compared with the theoretical model – potential flow. The velocity of the freestream has been evaluated by measurement of the frequency of the shedding vortices behind the standing cylinder in the regime of the Kármán vortex street. In the regime of the Kármán vortex street the Reynolds numbers were Re = 110 a 120. The known relations between Stouhal and Reynolds numbers were used.
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Annular Jets and Annular Impinging Jets
Turek, Tomáš ; Trávníček, Zdeněk ; Šafařík, Pavel ; Tesař, Václav
A near field of annular jets and annular impinging jets is experimentally investigated at three inner/outer diameter ratios 0.84, 0.90 and 0.95. Time-mean velocity profiles are evaluated, and three main flow field zones are distinguished – in agreement with the literature, namely the initial merging zone, the intermediate one, and the fully merged one. A distribution of the pressure on the impingement wall is measured for various nozzle-to-wall distances. Two basic annular impinging jet regimes are clearly distinguished, with either small or large recirculation bubbles. Moreover, a hysteretic behavior has been identified under specific parameters.
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