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Effect of the Number of Leaves in Submerged Aquatic Plants on Stream Flow Dynamics

1
School of Civil Engineering, Tianjin University, Tianjin 300072, China
2
State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China
3
School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin 150030, China
4
Key Laboratory of Effective Utilization of Agricultural Water Resources of Ministry of Agriculture, Northeast Agricultural University, Harbin 150030, China
5
Heilongjiang Provincial Key Laboratory of Water Resources and Water Conservancy Engineering in Cold Region, Northeast Agricultural University, Harbin 150030, China
*
Author to whom correspondence should be addressed.
Water 2019, 11(7), 1448; https://doi.org/10.3390/w11071448
Received: 12 June 2019 / Revised: 5 July 2019 / Accepted: 9 July 2019 / Published: 13 July 2019
(This article belongs to the Section Hydraulics)
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PDF [2444 KB, uploaded 13 July 2019]
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Abstract

The main purpose of this study is to investigate the effects of aquatic plants with no leaves (L0), 4 leaves (L4), 8 leaves (L8), and 12 leaves (L12) on the mean streamwise velocity, turbulence structure, and Manning’s roughness coefficient. The results show that the resistance of submerged aquatic plants to flow velocity is discontinuous between the lower aquatic plant layer and the upper free water layer. This leads to the difference of flow velocity between the upper and lower layers. An increase of the number of leaves leads to an increase in the flow velocity gradient in the upper non-vegetation area and a decrease in the flow velocity in the lower vegetation area. In addition, aquatic plants induce a momentum exchange near the top of the plant and increase the Reynold’s stress and turbulent kinetic energy. However, because of the inhibition of leaf area on the momentum exchange, the Reynold’s stress and turbulent kinetic energy increase first and then decrease with the increase in the number of leaves. Quadrant analysis shows that ejection and sweep play a dominant role in momentum exchange. Aquatic plants can also increase the Reynold’s stress by increasing the ejection and sweep. The Manning’s roughness coefficient increases with the increasing number of leaves. View Full-Text
Keywords: submerged flexible vegetation; flow velocity; Reynold’s stress; turbulent kinetic energy; Manning’s roughness coefficient submerged flexible vegetation; flow velocity; Reynold’s stress; turbulent kinetic energy; Manning’s roughness coefficient
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Yan, P.; Tian, Y.; Lei, X.; Fu, Q.; Li, T.; Li, J. Effect of the Number of Leaves in Submerged Aquatic Plants on Stream Flow Dynamics. Water 2019, 11, 1448.

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