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Open AccessEditor’s ChoiceReview

A Review on Hydrodynamics of Free Surface Flows in Emergent Vegetated Channels

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Department of Civil Engineering, Central Institute of Technology Kokrajhar, Kokrajhar 783370, Assam, India
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Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
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Department of Civil and Environmental Engineering, University of Windsor, Windsor, ON N9B 3P4, Canada
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School of Engineering, Faculty of Engineering and Informatics, University of Bradford, Bradford BD7 1DP, UK
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CERIS—Civil Engineering Research and Innovation for Sustainability, Av. Rovisco Pais, 1049-003 Lisboa, Portugal
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CERIS and Department of Civil Engineering, Architecture and Georesources, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
*
Authors to whom correspondence should be addressed.
Water 2020, 12(4), 1218; https://doi.org/10.3390/w12041218
Received: 27 February 2020 / Revised: 20 March 2020 / Accepted: 16 April 2020 / Published: 24 April 2020
This review paper addresses the structure of the mean flow and key turbulence quantities in free-surface flows with emergent vegetation. Emergent vegetation in open channel flow affects turbulence, flow patterns, flow resistance, sediment transport, and morphological changes. The last 15 years have witnessed significant advances in field, laboratory, and numerical investigations of turbulent flows within reaches of different types of emergent vegetation, such as rigid stems, flexible stems, with foliage or without foliage, and combinations of these. The influence of stem diameter, volume fraction, frontal area of stems, staggered and non-staggered arrangements of stems, and arrangement of stems in patches on mean flow and turbulence has been quantified in different research contexts using different instrumentation and numerical strategies. In this paper, a summary of key findings on emergent vegetation flows is offered, with particular emphasis on: (1) vertical structure of flow field, (2) velocity distribution, 2nd order moments, and distribution of turbulent kinetic energy (TKE) in horizontal plane, (3) horizontal structures which includes wake and shear flows and, (4) drag effect of emergent vegetation on the flow. It can be concluded that the drag coefficient of an emergent vegetation patch is proportional to the solid volume fraction and average drag of an individual vegetation stem is a linear function of the stem Reynolds number. The distribution of TKE in a horizontal plane demonstrates that the production of TKE is mostly associated with vortex shedding from individual stems. Production and dissipation of TKE are not in equilibrium, resulting in strong fluxes of TKE directed outward the near wake of each stem. In addition to Kelvin–Helmholtz and von Kármán vortices, the ejections and sweeps have profound influence on sediment dynamics in the emergent vegetated flows. View Full-Text
Keywords: turbulence; emergent vegetation; flexible vegetation; rigid vegetation; coherent structures; shear layer turbulence; emergent vegetation; flexible vegetation; rigid vegetation; coherent structures; shear layer
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MDPI and ACS Style

Maji, S.; Hanmaiahgari, P.R.; Balachandar, R.; Pu, J.H.; Ricardo, A.M.; Ferreira, R.M.L. A Review on Hydrodynamics of Free Surface Flows in Emergent Vegetated Channels. Water 2020, 12, 1218. https://doi.org/10.3390/w12041218

AMA Style

Maji S, Hanmaiahgari PR, Balachandar R, Pu JH, Ricardo AM, Ferreira RML. A Review on Hydrodynamics of Free Surface Flows in Emergent Vegetated Channels. Water. 2020; 12(4):1218. https://doi.org/10.3390/w12041218

Chicago/Turabian Style

Maji, Soumen; Hanmaiahgari, Prashanth R.; Balachandar, Ram; Pu, Jaan H.; Ricardo, Ana M.; Ferreira, Rui M.L. 2020. "A Review on Hydrodynamics of Free Surface Flows in Emergent Vegetated Channels" Water 12, no. 4: 1218. https://doi.org/10.3390/w12041218

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