Non-rotational coherent structures in the flow with different degree of turbulence

0480033 - ÚT 2018 eng C - Conference Paper (international conference)
Kellnerová, Radka - Jurčáková, Klára - Nosek, Štěpán - Jaňour, Zbyněk
Non-rotational coherent structures in the flow with different degree of turbulence.
[Symposium on Boundary Layers and Turbulence /22./. Salt Lake City (US), 20.06.2016-24.06.2016]
R&D Projects: GA ČR GA15-18964S
Institutional support: RVO:61388998
Keywords : coherent structure * turbulence * PIV * correlation * quadrant analysis
Subject RIV: DG - Athmosphere Sciences, Meteorology
https://ams.confex.com/ams/32AgF22BLT3BG/webprogram/Paper296008.html

The coherent structures are not satisfactorily defined for a very complex atmospheric flow. The features with a rotational motion, namely the vortices and hairpins, are mostly considered as a typical coherent pattern. In the turbulent flow, however, the non-rotational transient phenomenon may play a crucial role. The boundary layer dynamics above surfaces of various roughness was measured in the wind-channel by 2D 2C TR-PIV. The data recorded with the high sampling frequency were analysed by means of coherence detection methods. Firstly, the spatial correlation of the longitudinal and vertical velocity component is calculated and a tilt angle of the area with significant correlation coefficient is retrieved. Secondly, the Quadrant analyses applied to the momentum flux at each snapshot revealed that the spatially compact regions of the uniform sweep and ejection events contained up to 80% of the total momentum flux.
Permanent Link: http://hdl.handle.net/11104/0279392