Mean flow and turbulence structure of open-channel flow through non-emergent vegetation

Fabián Löpez, Marcelo H. Garcia

Research output: Contribution to journalArticle

Abstract

The ability of turbulence models, based on two equation closure schemes (the k-ε and the k-ω formulations) to compute the mean flow and turbulence structure in open channels with rigid, nonemergent vegetation is analyzed. The procedure, developed by Raupach and Shaw (1982), for atmospheric flows over plant canopies is used to transform the 3D problem into a more tractable 1D framework by averaging the conservation laws over space and time. With this methodology, form/drag related terms arise as a consequence of the averaging procedure, and do not need to be introduced artificially in the governing equations. This approach resolves the apparent ambiguity in previously reported values of the drag-related weighting coefficients in the equations for the turbulent kinetic energy and dissipation rates. The working hypothesis for the numerical models is that the flux gradient approximation applies to spatial/temporal averaged conservation laws, so that the eddy viscosity concept can be used. Numerical results are compared against experimental observations, including mean velocities, turbulence intensities, Reynolds stresses, and different terms in the turbulent kinetic energy budget. The models are used to further estimate vegetation-induced flow resistance. In agreement with field observations, Manning's coefficient is almost uniform for some critical plant density and then increases linearly.

Original languageEnglish (US)
Pages (from-to)392-402
Number of pages11
JournalJournal of Hydraulic Engineering
Volume127
Issue number5
DOIs
StatePublished - May 1 2001
Externally publishedYes

Fingerprint

Open channel flow
open channel flow
Kinetic energy
Drag
Conservation
Turbulence
turbulence
kinetic energy
drag
vegetation
Turbulence models
Numerical models
Viscosity
Fluxes
energy budget
dissipation
eddy
transform
viscosity
canopy

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Water Science and Technology
  • Mechanical Engineering

Cite this

Mean flow and turbulence structure of open-channel flow through non-emergent vegetation. / Löpez, Fabián; Garcia, Marcelo H.

In: Journal of Hydraulic Engineering, Vol. 127, No. 5, 01.05.2001, p. 392-402.

Research output: Contribution to journalArticle

@article{bf47485668214f7c8f6c0f1b3baf3cd2,
title = "Mean flow and turbulence structure of open-channel flow through non-emergent vegetation",
abstract = "The ability of turbulence models, based on two equation closure schemes (the k-ε and the k-ω formulations) to compute the mean flow and turbulence structure in open channels with rigid, nonemergent vegetation is analyzed. The procedure, developed by Raupach and Shaw (1982), for atmospheric flows over plant canopies is used to transform the 3D problem into a more tractable 1D framework by averaging the conservation laws over space and time. With this methodology, form/drag related terms arise as a consequence of the averaging procedure, and do not need to be introduced artificially in the governing equations. This approach resolves the apparent ambiguity in previously reported values of the drag-related weighting coefficients in the equations for the turbulent kinetic energy and dissipation rates. The working hypothesis for the numerical models is that the flux gradient approximation applies to spatial/temporal averaged conservation laws, so that the eddy viscosity concept can be used. Numerical results are compared against experimental observations, including mean velocities, turbulence intensities, Reynolds stresses, and different terms in the turbulent kinetic energy budget. The models are used to further estimate vegetation-induced flow resistance. In agreement with field observations, Manning's coefficient is almost uniform for some critical plant density and then increases linearly.",
author = "Fabi{\'a}n L{\"o}pez and Garcia, {Marcelo H.}",
year = "2001",
month = "5",
day = "1",
doi = "10.1061/(ASCE)0733-9429(2001)127:5(392)",
language = "English (US)",
volume = "127",
pages = "392--402",
journal = "Journal of Hydraulic Engineering",
issn = "0733-9429",
publisher = "American Society of Civil Engineers (ASCE)",
number = "5",

}

TY - JOUR

T1 - Mean flow and turbulence structure of open-channel flow through non-emergent vegetation

AU - Löpez, Fabián

AU - Garcia, Marcelo H.

PY - 2001/5/1

Y1 - 2001/5/1

N2 - The ability of turbulence models, based on two equation closure schemes (the k-ε and the k-ω formulations) to compute the mean flow and turbulence structure in open channels with rigid, nonemergent vegetation is analyzed. The procedure, developed by Raupach and Shaw (1982), for atmospheric flows over plant canopies is used to transform the 3D problem into a more tractable 1D framework by averaging the conservation laws over space and time. With this methodology, form/drag related terms arise as a consequence of the averaging procedure, and do not need to be introduced artificially in the governing equations. This approach resolves the apparent ambiguity in previously reported values of the drag-related weighting coefficients in the equations for the turbulent kinetic energy and dissipation rates. The working hypothesis for the numerical models is that the flux gradient approximation applies to spatial/temporal averaged conservation laws, so that the eddy viscosity concept can be used. Numerical results are compared against experimental observations, including mean velocities, turbulence intensities, Reynolds stresses, and different terms in the turbulent kinetic energy budget. The models are used to further estimate vegetation-induced flow resistance. In agreement with field observations, Manning's coefficient is almost uniform for some critical plant density and then increases linearly.

AB - The ability of turbulence models, based on two equation closure schemes (the k-ε and the k-ω formulations) to compute the mean flow and turbulence structure in open channels with rigid, nonemergent vegetation is analyzed. The procedure, developed by Raupach and Shaw (1982), for atmospheric flows over plant canopies is used to transform the 3D problem into a more tractable 1D framework by averaging the conservation laws over space and time. With this methodology, form/drag related terms arise as a consequence of the averaging procedure, and do not need to be introduced artificially in the governing equations. This approach resolves the apparent ambiguity in previously reported values of the drag-related weighting coefficients in the equations for the turbulent kinetic energy and dissipation rates. The working hypothesis for the numerical models is that the flux gradient approximation applies to spatial/temporal averaged conservation laws, so that the eddy viscosity concept can be used. Numerical results are compared against experimental observations, including mean velocities, turbulence intensities, Reynolds stresses, and different terms in the turbulent kinetic energy budget. The models are used to further estimate vegetation-induced flow resistance. In agreement with field observations, Manning's coefficient is almost uniform for some critical plant density and then increases linearly.

UR - http://www.scopus.com/inward/record.url?scp=18244431926&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=18244431926&partnerID=8YFLogxK

U2 - 10.1061/(ASCE)0733-9429(2001)127:5(392)

DO - 10.1061/(ASCE)0733-9429(2001)127:5(392)

M3 - Article

AN - SCOPUS:18244431926

VL - 127

SP - 392

EP - 402

JO - Journal of Hydraulic Engineering

JF - Journal of Hydraulic Engineering

SN - 0733-9429

IS - 5

ER -