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Oblique collisions of non-rotating spherical particles with a wall
Chára, Zdeněk ; Vlasák, Pavel ; Kysela, Bohuš
In the present paper non-rotating particle-wall collisions were experimentally investigated. By means of the PIV method a velocity field around falling spheres was analyzed. It was shown that the wake behind the particle which approached a bed in non-normal direction was asymmetrical and after the impact the wake passed the particle only along one side. This non-symmetrical velocity field resulted in additional forces which pushed the particle to an opposite direction than was the direction of the particle motion just after the impact.
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Proudění v okolí Ahmedova tělesa
Uruba, Václav ; Sedlák, K.
Byl experimentálně vyšetřován úplav za rovinným Ahmedovým tělesem v kanále. Zvláštní pozornost byla věnována oblasti proudění nad horní zadní částí modelu, odtržení mezní vrstvy od střechy a vytváření úplavu. Podrobně byla sledována volná smyková oblast v horní části úplavu. Byby studovány varianty s úhlen zadní části modelu = 25° a 35°. Úhel 25° vykazuje více-méně přilnuté proudění, zatímco úhel 35° vytváří odtržení v oblasti zadní části modelu.
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Smoke visualization of jet and wake flows
Trávníček, Zdeněk
Flow visualization, as a part of experimental fluid mechanics, is a typical initial step of many experimental studies. It can contribute significantly to the understanding of mechanisms involved in flow fields. Moreover, it can be helpful in the selection of the flow parameters and regions of interest for local and detail point measurements. The visualization can be very beneficial for a precise adjustment of a chosen flow field pattern in a test section if alternative flow field modes are possible. Typical case is a bistable and hysteretic behavior of complex flows. The paper shows a few cases of complex jet and wake flows, namely impinging jets from standard and special nozzles (round and slot nozzles, annular nozzle with a fluidic or acoustic control, two-slot nozzle, and slot nozzle with the Coanda effect), and a non-isothermal wake flow behind a cylinder in the cross flow.
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