Velocity profiles in vegetated open-channel flows: combined effects of multiple mechanisms

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37 Citations (Scopus)

Abstract

Vertical profile of longitudinal velocity in vegetated channels reflects complex mechanics of flow-vegetation interactions and determines the bulk flow velocity and flow rate. Most available models of velocity profiles in vegetated channels are based on a single physical concept that underpins theoretical considerations and data interpretation. However, measured velocity profiles suggest that the
use of a single concept is not sufficient to cover all possible scenarios of flow-vegetation interactions. As a result, a number of models in which different concepts are applied to different flow regions have been recently developed. Within this framework, the overall velocity profile is represented with a set of linked segments. Although such segment-based models have improved velocity profile description, there is a need for more robust approaches and better analytical formulations. This paper proposes a new approach where a vertical velocity profile in vegetated channels is modelled as a linear superposition of four concepts: (1) uniform velocity distribution, (2) mixing layer analogy and a
hyperbolic tangent profile, (3) boundary layer concept and a logarithmic profile, and (4) wake function concept. In contrast to the segment-based models, the proposed analytical expression combines these concepts simultaneously over the whole flow depth allowing significant overlaps of the momentum transport and turbulence production mechanisms. The model is tested using extensive laboratory experiments.
Original languageEnglish
Pages (from-to)1021-1032
Number of pages12
JournalJournal of Hydraulic Engineering
Volume139
Issue number10
Early online date23 May 2013
DOIs
Publication statusPublished - 1 Oct 2013

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Open channel flow
open channel flow
velocity profile
vegetation
data interpretation
flow velocity
vertical profile
mechanics
Velocity distribution
momentum
Flow velocity
boundary layer
turbulence
effect
Momentum
Mechanics
Boundary layers
Turbulence
Flow rate

Keywords

  • Aquatic vegetation
  • Boundary layer
  • Hydraulic resistance
  • Mixing layer
  • Vegetated open-channel flow
  • Vertical velocity profile
  • Wake function

Cite this

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title = "Velocity profiles in vegetated open-channel flows: combined effects of multiple mechanisms",
abstract = "Vertical profile of longitudinal velocity in vegetated channels reflects complex mechanics of flow-vegetation interactions and determines the bulk flow velocity and flow rate. Most available models of velocity profiles in vegetated channels are based on a single physical concept that underpins theoretical considerations and data interpretation. However, measured velocity profiles suggest that theuse of a single concept is not sufficient to cover all possible scenarios of flow-vegetation interactions. As a result, a number of models in which different concepts are applied to different flow regions have been recently developed. Within this framework, the overall velocity profile is represented with a set of linked segments. Although such segment-based models have improved velocity profile description, there is a need for more robust approaches and better analytical formulations. This paper proposes a new approach where a vertical velocity profile in vegetated channels is modelled as a linear superposition of four concepts: (1) uniform velocity distribution, (2) mixing layer analogy and ahyperbolic tangent profile, (3) boundary layer concept and a logarithmic profile, and (4) wake function concept. In contrast to the segment-based models, the proposed analytical expression combines these concepts simultaneously over the whole flow depth allowing significant overlaps of the momentum transport and turbulence production mechanisms. The model is tested using extensive laboratory experiments.",
keywords = "Aquatic vegetation, Boundary layer, Hydraulic resistance, Mixing layer, Vegetated open-channel flow, Vertical velocity profile, Wake function",
author = "Nina Nikora and Vladimir Nikora and Tom O'Donoghue",
note = "Acknowledgments The research was partly supported by the Leverhulme Trust, grant F/00152/Z “Biophysics of flow-plant interactions in aquatic systems,” FP7-People-2012-ITN grant HYTECH, GA-2012-316546, and also stimulated by the Scientific Research Network WO.027p11N. Journal of Hydraulic Engineering / Volume 140 Issue 12 - December 2014: Erratum for “Velocity Profiles in Vegetated Open-Channel Flows: Combined Effects of Multiple Mechanisms” by Nina Nikora, Vladimir Nikora, and Tom O’Donoghue https://doi.org/10.1061/(ASCE)HY.1943-7900.0000948",
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N1 - Acknowledgments The research was partly supported by the Leverhulme Trust, grant F/00152/Z “Biophysics of flow-plant interactions in aquatic systems,” FP7-People-2012-ITN grant HYTECH, GA-2012-316546, and also stimulated by the Scientific Research Network WO.027p11N. Journal of Hydraulic Engineering / Volume 140 Issue 12 - December 2014: Erratum for “Velocity Profiles in Vegetated Open-Channel Flows: Combined Effects of Multiple Mechanisms” by Nina Nikora, Vladimir Nikora, and Tom O’Donoghue https://doi.org/10.1061/(ASCE)HY.1943-7900.0000948

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N2 - Vertical profile of longitudinal velocity in vegetated channels reflects complex mechanics of flow-vegetation interactions and determines the bulk flow velocity and flow rate. Most available models of velocity profiles in vegetated channels are based on a single physical concept that underpins theoretical considerations and data interpretation. However, measured velocity profiles suggest that theuse of a single concept is not sufficient to cover all possible scenarios of flow-vegetation interactions. As a result, a number of models in which different concepts are applied to different flow regions have been recently developed. Within this framework, the overall velocity profile is represented with a set of linked segments. Although such segment-based models have improved velocity profile description, there is a need for more robust approaches and better analytical formulations. This paper proposes a new approach where a vertical velocity profile in vegetated channels is modelled as a linear superposition of four concepts: (1) uniform velocity distribution, (2) mixing layer analogy and ahyperbolic tangent profile, (3) boundary layer concept and a logarithmic profile, and (4) wake function concept. In contrast to the segment-based models, the proposed analytical expression combines these concepts simultaneously over the whole flow depth allowing significant overlaps of the momentum transport and turbulence production mechanisms. The model is tested using extensive laboratory experiments.

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