This study reports on experimentally observed rare near-wall reverse flow events in a fully developed turbulent flat plate boundary layer at zero pressure gradient with Reynolds numbers between Reθ≈2500 and Reθ≈8000 (Reτ≈800–2400). The reverse flow events are captured using high magnification particle image velocimetry sequences with record lengths varying from 50 000 to 126 000 samples. Time resolved particle image sequences allow singular reverse flow events to be followed over several time steps whereas long records of nearly statistically independent samples provide a variety of single snapshots at a higher spatial resolution. The probability of occurrence lies in the order of 0.012–0.018% which matches predictions from direct numerical simulations (DNS). The typical size of the reverse flow bubble is about 30 wall units in length and 5 wall units in height which agrees well with similar observations made in existing DNS data.
|Original language||English (US)|
|Number of pages||9|
|Journal||Experimental Thermal and Fluid Science|
|State||Published - Feb 2018|
Bibliographical noteFunding Information:
The authors would like to acknowledge the financial support provided through the European High performance Infrastructures in Turbulence (EuHIT) Transnational Access Program (European Grant Agreement No. 312278 , www.euhit.org ). The LML members also acknowledge the regional councils of Nord-Pas-de-Calais, the CNRS of France and the European Community for providing funding for the refurbishment of the wind tunnel facility through the CISIT project.
- Boundary layer
- Flow reversal
- Particle image velocimetry
- Turbulence statistics
- Wall shear stress