Abstract
This paper studies the effects of different types and configurations of double layer vegetation on the flow of open channels. The vegetation is simulated through cylindrical dowels with a diameter of 6.35 mm and heights of 10 and 20 cm, which represent short and tall dowels, respectively. Profiles for instantaneous velocities were obtained by acoustic Doppler velocimetry (ADV) at different locations around vegetation with multiple staggered and linear formations. The experiment covers a wide range of sparse to dense vegetation configurations. Furthermore, different flow depths were selected to simulate fully submerged cases for short vegetation and to capture the inflection of velocity over the mixing region between short and tall dowels. The results reveal that the velocity profile is mostly uniform at the depth of short vegetation in different configurations with various densities. The velocity starts to increase in the region near the top edge of short vegetation, followed by a significant increase through the height of tall vegetation to the free surface. Generally, the flow velocity behind the vegetation layer is significantly smaller than that in free regions adjacent to short and tall vegetation. The overall idea of the present study was to simulate the same sets of vegetation configurations using a model with mesh sensitivity analysis to capture inflections over the short vegetation region. The experimental investigations with a numerical study were explored for double layer vegetation, which was corroborated and found to have good agreement for different vegetation configurations.
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Data Availability Statement
Some or all data, models, or code used during the study were provided by a third party. Data used during the study are available from the corresponding author by request.
Acknowledgments
The authors would like to thank the staff of Nanjing Hydraulic Research Institute for their support and time during the experiments and acknowledge the financial support of the Research Development Fund (RDF-15-01-10) and Key Program Special Fund (KSF-E-17) of XJTLU.
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Journal of Hydrologic Engineering
Volume 25 • Issue 2 • February 2020
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©2019 American Society of Civil Engineers.
History
Received: Sep 28, 2018
Accepted: Aug 23, 2019
Published online: Nov 26, 2019
Published in print: Feb 1, 2020
Discussion open until: Apr 26, 2020
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