Abstract
Free-surface shallow shear flows behind a vertical splitter plate were studied in a tilted laboratory flume with a rectangular cross-section. The bed and sidewalls, made of glass, were hydraulically smooth. The vertical flow confinement (i.e., flow depth) was modified by changing the total flow rate Q (14, 30, 60, and 120 l s-1). At the flume entrance, for each Q-value, the flow partition from either side of the splitter plate was also varied to cover a wide range of the shear parameter λ = (U-2-U-1)/(U-2+U-1), where U1 and U-2 are two velocities characterizing the low-speed and high-speed streams, respectively (with λ = 0 to 1.0). The focus of the study was on clarifying the effects on the large-scale flow structures of: (i) vertical flow confinement; (ii) bed-friction; and (iii) λ-parameter. Particular attention was paid to the emergence and development of: quasi-2D Kelvin-Helmholtz-type Coherent Structures (KHCSs); 3D Large-Scale-Motions (LSMs), e.g., packets of hairpin vortices and associated burst events; and 3D Very-Large-Scale-Motions (VLSMs), which are long meandering streamwise counter-rotating vortices. It was found that in the near-field region, the emergence and length-scales of the KHCSs were independent of (i) and (ii), but were essentially controlled by (iii). For instance, the KHCSs cannot form if λ <~ 0.3. In the far-field region, the effect of λ decreases while that of bed-friction number S increases. For S > ~ 0.04, KHCSs are fully longitudinally stretched. LSMs/VLSMs development are strongly influenced by splitter effects as well as the magnitude of velocity shear, particularly when λ > 0.3.
Original language | English |
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Title of host publication | Proceedings of the 39th IAHR World Congress |
Subtitle of host publication | From Snow to Sea |
Editors | Miguel Ortega-Sánchez |
Publisher | IAHR |
Chapter | 3 |
Pages | 1584-1589 |
Number of pages | 6 |
ISBN (Print) | 978-90-832612-1-8 |
DOIs | |
Publication status | Published - 19 Jun 2022 |
Event | 39th IAHR World Congress, 2022 - Granada, Spain Duration: 19 Jun 2022 → 24 Jun 2022 |
Publication series
Name | Proceedings of the IAHR World Congress |
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Publisher | IAHR |
ISSN (Print) | 2521-7119 |
ISSN (Electronic) | 2521-716x |
Conference
Conference | 39th IAHR World Congress, 2022 |
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Country/Territory | Spain |
City | Granada |
Period | 19/06/22 → 24/06/22 |
Bibliographical note
Funding Information:The experiments were carried out in the HHLab with the support of Fabien Thollet and Adrien Bonnefoy.
Proceedings of the IAHR World Congress, Pages 1584 - 1589 2022, 39th IAHR World Congress, 2022 Granada 19 June 2022 through 24 June 2022, Code 299039
Publisher Copyright: © 2022 IAHR.
ISSN: 25217119
Keywords
- Coherent structures
- Kelvin-Helmholtz instability
- Large-scale-motions
- Mixing layer
- Very-large-scale-motions