Whalley, RD, Dennis, DJC 
ORCID: 0000-0003-0214-7885, Graham, MD and Poole, RJ ORCID: 0000-0001-6686-4301
(2019)
An experimental investigation into spatiotemporal intermittencies in turbulent channel flow close to transition.
EXPERIMENTS IN FLUIDS, 60 (6).
Abstract
Abstract: Experiments are presented to characterize low- and high-drag turbulence events in channel flows close to transition, which last for a certain duration, at friction Reynolds numbers ranging from Reτ= 70–100. The spatiotemporal intermittencies are identified by applying conditional sampling techniques to simultaneously acquired wall shear stress and velocity data using either single-point laser Doppler velocimetry (LDV) or stereoscopic particle image velocimetry (SPIV). It is shown that ensemble-averaged streamwise velocity during intervals of low drag fall close to a recently discovered exact coherent state (ECS), in agreement with recent direct numerical simulation (DNS) results. The low-drag intervals are characterized by a low-stress streak which is flanked on either side by a streamwise vortex, forming a counter-rotating vortex pair. Ensemble-averaged streamwise velocity during intervals of high drag fall further below the Prandtl–von Kármán log-law with increasing Reynolds number. Generally, higher levels of turbulence intensity are observed during intervals of low drag when compared to similar intervals of high drag.
| Item Type: | Article |
|---|---|
| Depositing User: | Symplectic Admin |
| Date Deposited: | 24 Jun 2019 09:20 |
| Last Modified: | 19 Jan 2023 00:39 |
| DOI: | 10.1007/s00348-019-2739-9 |
| Open Access URL: | https://link.springer.com/article/10.1007/s00348-0... |
| Related URLs: | |
| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3047221 |
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