Abstract
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.
Highlights
Vegetation is ubiquitous in rivers, estuaries, lake shores and some coastal areas [1]
Flow velocity decreases within the vegetation, which can lead to flow velocity decreases within the vegetation, which can lead to deposition of sediment deposition of sediment which accelerates with the time and acts like a catalyst to the larger which accelerates with the and[37,39]
It was well accepted that the presence of emergent vegetation in the rivers and open channel flows has a significant role on mean velocity, turbulence levels, coherent structures and the accompanying mass and momentum fluxes at the boundary between emergent vegetation and an open channel
Summary
Soumen Maji 1 , Prashanth Reddy Hanmaiahgari 2, * , Ram Balachandar 3 , Jaan H. Ricardo 5 and Rui M.L. Ferreira 6.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
