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Diagnostika toku v kanále za náhlým rozšířením.
Tihon, Jaroslav ; Pantzali, M. ; Havlica, Jaromír
The backward-facing step flow is studied by measuring the instantaneous wall shear rate along the channel centerline. A two-strip electrodiffusion probe is applied to provide information on the flow direction in the near-wall region. The wall shear rate profiles behind the step are measured and the position of reattachment point detected. The Reynolds numbers examined (Reh from 30 to 1800) cover the laminar, transient and beginning of turbulent flow regime. The results are found to be in a good agreement with the experimental and numerical data previously published for the same channel geometry (ER=2, AR=25).
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Vortex Structures in an Excited Impinging Jet Flow
Vejražka, Jiří ; Tihon, Jaroslav ; Cvetković, D.
The behavior of vortex structures is studied in an impinging jet of Reynolds number 10 000. The effect of the modulation of the nozzle exit velocity on the flow structure is studied by means of hot-wire anemometry. It is found that the velocity field can be modified by excitations of a wide range of frequencies. In most cases the excitation yields formation of large vortices, which provoke an unsteady flow separation at their impact onto the wall. The excitation at higher frequencies suppresses the roll-up of large eddies. The velocity fluctuations near the wall are then suppressed and the flow separation disappears. The effect is documented by phase averaging for the low nozzle-to-plate spacing. The time-averaged measurements show that the unsteady flow separation can be suppressed even for nozzle-to-plate spacing up to eight diameters.
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Dynamika solitárních vln při filmovém toku kapalin
Tihon, Jaroslav
The regular solitary waves on the surface of a liquid film flowing down an inclined stationary plate were excited by means of the flow rate pulsations. The results of experimental investigations provided the basic characteristics of surface waves and confirmed the existence of a small backflow region located just in front of the solitary waves.
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