Boothroyd_et_al-2017-Water_Resources_Research.pdf (2.2 MB)
Modeling complex flow structures and drag around a submerged plant of varied posture
journal contribution
posted on 2017-04-28, 08:14 authored by Richard J. Boothroyd, Richard J. Hardy, Jeff Warburton, Tim MarjoribanksTim MarjoribanksAlthough vegetation is present in many rivers, the bulk of past work concerned with modeling the influence of vegetation on flow has considered vegetation to be morphologically simple and has generally neglected the complexity of natural plants. Here we report on a combined flume and numerical model experiment which incorporates time-averaged plant posture, collected through terrestrial laser scanning, into a computational fluid dynamics model to predict flow around a submerged riparian plant. For three depth-limited flow conditions (Reynolds number = 65,000–110,000), plant dynamics were recorded through high-definition video imagery, and the numerical model was validated against flow velocities collected with an acoustic Doppler velocimeter. The plant morphology shows an 18% reduction in plant height and a 14% increase in plant length, compressing and reducing the volumetric canopy morphology as the Reynolds number increases. Plant shear layer turbulence is dominated by Kelvin-Helmholtz type vortices generated through shear instability, the frequency of which is estimated to be between 0.20 and 0.30 Hz, increasing with Reynolds number. These results demonstrate the significant effect that the complex morphology of natural plants has on in-stream drag, and allow a physically determined, species-dependent drag coefficient to be calculated. Given the importance of vegetation in river corridor management, the approach developed here demonstrates the necessity to account for plant motion when calculating vegetative resistance.
Funding
Richard J. Boothroyd was funded under Natural Environmental Research Council (NERC) PhD Studentship 1313876. The flume experiments were funded through NERC grant NE/F010060/1.
History
School
- Architecture, Building and Civil Engineering
Published in
Water Resources ResearchVolume
53Issue
4Pages
2877–2901Citation
BOOTHROYD, R.J., 2017. Modeling complex flow structures and drag around a submerged plant of varied posture. Water Resources Research, 53 (4), pp. 2877–2901.Publisher
American Geophysical Union © The AuthorsVersion
- VoR (Version of Record)
Publisher statement
This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/ by/4.0/Acceptance date
2017-03-10Publication date
2017-03-17Copyright date
2017Notes
This is an Open Access Article. It is published by the American Geophysical Union under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/ISSN
0043-1397eISSN
1944-7973Publisher version
Language
- en