Flow structure in compound open-channel flows in the presence of transverse currents

Sébastien Proust* (Corresponding Author), Vladimir Nikora

*Corresponding author for this work

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2 Citations (Scopus)
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Abstract

The structure of free-surface flows is experimentally investigated in a laboratory flume with a compound cross-section consisting of a central main channel (MC) and two adjacent floodplains (FPs). The study focuses on the effects of transverse currents on: (i) mixing layers and quasi-two-dimensional coherent structures at the interfaces between MC and FPs; (ii) secondary currents developing across the channel; and (iii) large and very-large-scale motions that were recently observed in non-compound open channel flows. Transverse currents represent spanwise depth- and time-averaged flow from MC to FPs or vice versa. The study is based on one-point and two-point ADV measurements. Streamwise non-uniform flows are generated by imposing an imbalance in the discharge distribution between MC and FPs at the flume entrance, keeping the total flow rate the same for all scenarios. It is shown that even small transverse currents can be very effective in flow modification, as they can significantly displace the mixing layer, shear-layer turbulence, and coherent structures towards MC or FP, depending on the current direction. They can also alter the distribution and strength of the secondary currents. The interactions of quasi-two-dimensional coherent structures, very-large-scale motions, and secondary currents at different conditions are also part of this study.

Original languageEnglish
Article number05024
Number of pages8
JournalE3S Web of Conferences
Volume40
DOIs
Publication statusPublished - 5 Sept 2018
Event9th International Conference on Fluvial Hydraulics, River Flow 2018 - Lyon-Villeurbanne, France
Duration: 5 Sept 20188 Sept 2018

Bibliographical note

We are grateful to Fabien Thollet and Alexis Buffet for their help during the experiments. This research work is funded by the French National Research Agency through the FlowRes project (https://flowres.irstea.fr/en/), under Grant N° ANR-14-CE03-0010.

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