Visualization of secondary flow in a corner of a channel

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F49777513%3A23210%2F19%3A43959511" target="_blank" >RIV/49777513:23210/19:43959511 - isvavai.cz</a>

Výsledek na webu

<a href="https://aip.scitation.org/doi/abs/10.1063/1.5138615" target="_blank" >https://aip.scitation.org/doi/abs/10.1063/1.5138615</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1063/1.5138615" target="_blank" >10.1063/1.5138615</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Visualization of secondary flow in a corner of a channel

Popis výsledku v původním jazyce

We report observation of secondary flow in one corner of developing channel air flow. Length of the channel, i.e. length of boundary layer, is 400?mm, which is 3.2 times the channel cross-sectional size. Three components of velocity are measured by using a Stereo Particle Image Velocimetry (PIV) technique in the measurement area of size 24×22?mm, which is perpendicular to the direction of main flow in the channel. The Reynolds number based on the length of the channel ranged from 4·104 to 8·105 and has been controlled via imposed velocity. At low Reynolds number we observe a laminar corner vortex having at all velocities the same orientation. This symmetry breaking is probably caused by an imperfectness of the experimental device. At Reynolds number around 8·104 this vortex starts to slightly variate its strength and position causing transition of boundary layers into turbulence at Re = 1.1·105. At higher Re this laminar vortex disappears from the instantaneous velocity fields, but it is still apparent in the averaged ones. It gets smaller and another oppositely oriented vortex forms; note that the second vortex is not observed in the instantaneous velocity fields, only in the ensemble average. At even higher Re, this secondary flow structure is smaller than the turbulent boundary layers, but its shape of a pair of counter-rotating vortices is conserved probably being a seed for secondary flow between fully developed boundary layers reported in the literature for longer channels with fully developed flow.

Název v anglickém jazyce

Visualization of secondary flow in a corner of a channel

Popis výsledku anglicky

We report observation of secondary flow in one corner of developing channel air flow. Length of the channel, i.e. length of boundary layer, is 400?mm, which is 3.2 times the channel cross-sectional size. Three components of velocity are measured by using a Stereo Particle Image Velocimetry (PIV) technique in the measurement area of size 24×22?mm, which is perpendicular to the direction of main flow in the channel. The Reynolds number based on the length of the channel ranged from 4·104 to 8·105 and has been controlled via imposed velocity. At low Reynolds number we observe a laminar corner vortex having at all velocities the same orientation. This symmetry breaking is probably caused by an imperfectness of the experimental device. At Reynolds number around 8·104 this vortex starts to slightly variate its strength and position causing transition of boundary layers into turbulence at Re = 1.1·105. At higher Re this laminar vortex disappears from the instantaneous velocity fields, but it is still apparent in the averaged ones. It gets smaller and another oppositely oriented vortex forms; note that the second vortex is not observed in the instantaneous velocity fields, only in the ensemble average. At even higher Re, this secondary flow structure is smaller than the turbulent boundary layers, but its shape of a pair of counter-rotating vortices is conserved probably being a seed for secondary flow between fully developed boundary layers reported in the literature for longer channels with fully developed flow.

Druh

D - Stať ve sborníku

CEP obor

—

OECD FORD obor

10305 - Fluids and plasma physics (including surface physics)

Projekt

—

Návaznosti

S - Specificky vyzkum na vysokych skolach

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název statě ve sborníku

AIP Conference Proceedings

ISBN

978-0-7354-1936-0

ISSN

0094-243X

e-ISSN

1551-7616

Počet stran výsledku

6

Strana od-do

—

Název nakladatele

American Institute of Physics Inc.

Místo vydání

Neuveden

Místo konání akce

Plzeň

Datum konání akce

11. 6. 2019

Typ akce podle státní příslušnosti

WRD - Celosvětová akce

Kód UT WoS článku

—