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Article

Formation of Coherent Flow Structures beyond Vegetation Patches in Channel

1
Faculty of Civil Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran
2
School of Engineering, University of Northern British Columbia, Prince George, BC V2N 4Z9, Canada
*
Author to whom correspondence should be addressed.
Academic Editor: Achim A. Beylich
Water 2021, 13(20), 2812; https://doi.org/10.3390/w13202812
Received: 2 September 2021 / Revised: 30 September 2021 / Accepted: 5 October 2021 / Published: 10 October 2021
(This article belongs to the Special Issue Sediment Transport, Local Scour, and Fluvial Hydraulics)
By using model vegetation (e.g., synthetic bars), vortex structures in a channel with vegetation patches have been studied. It has been reported that vortex structures, including both the vertical and horizontal vortexes, may be produced in the wake in the channel bed with a finite-width vegetation patch. In the present experimental study, both velocity and TKE have been measured (via Acoustic Doppler Velocimeter—ADV) to study the formation of vortexes behind four vegetation patches in the channel bed. These vegetation patches have different dimensions, from the channel-bed fully covered patch to small-sized patches. Model vegetation used in this research is closely similar to vegetation in natural rivers with a gravel bed. The results show that, for a channel with a small patch (Lv/Dc = 0.44 and Dv/Dc = 0.33; where Lv and Dv are the length and width of patch and Dc is the channel width, respectively), both the flow passing through the patch and side flow around the patch have a considerable effect on the formation of flow structures beyond the patch. The results of further analysis via 3D classes of the bursting events show that the von Karman vortex street splits into two parts beyond the vegetation patch as the strong part near the surface and the weak part near the bed; while the middle part of the flow is completely occupied by the vertical vortex formed at a distance of 0.8–1 Hv beyond the vegetation patch, and thus, the horizontal vortexes cannot be detected in this region. The octant analysis is conducted for the coherent shear stress analysis that confirms the results of this experimental study. View Full-Text
Keywords: coherent flow structures; vegetation patch; von Karman vortex; octant analysis coherent flow structures; vegetation patch; von Karman vortex; octant analysis
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MDPI and ACS Style

Kazem, M.; Afzalimehr, H.; Sui, J. Formation of Coherent Flow Structures beyond Vegetation Patches in Channel. Water 2021, 13, 2812. https://doi.org/10.3390/w13202812

AMA Style

Kazem M, Afzalimehr H, Sui J. Formation of Coherent Flow Structures beyond Vegetation Patches in Channel. Water. 2021; 13(20):2812. https://doi.org/10.3390/w13202812

Chicago/Turabian Style

Kazem, Masoud, Hossein Afzalimehr, and Jueyi Sui. 2021. "Formation of Coherent Flow Structures beyond Vegetation Patches in Channel" Water 13, no. 20: 2812. https://doi.org/10.3390/w13202812

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