First- and Second-Order Closure Models for Wind in a Plant Canopy

Pinard, Jean-Paul; Wilson, John D.

doi:10.1175/1520-0450(2001)040<1762:fasocm>2.0.co;2

Cited by 57 publications

(36 citation statements)

References 7 publications

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“…Traditionally, vertically distributed single-point measurements of instantaneous velocity time series were used to investigate the mean drag-wind relationship (e.g., Cescatti and Marcolla 2004;Queck et al 2012). This traditional approach assumes that data are representative of spatially-averaged metrics of statistically stationary flow within and above a horizontally homogeneous canopy (Pinard and Wilson 2001). With these conditions, (2) is simplified as,…”

Section: Models Of Mean Canopy Drag and Traditional Estimates Of Locamentioning

confidence: 99%

“…An uncertainty of 5 % in the estimated u w can induce an error of 100 % in estimating its vertical gradient that balances the streamwise mean pressure gradient. In field studies for terrestrial canopies, the streamwise mean pressure gradient in (7) is usually neglected (e.g., Pinard and Wilson 2001;Cescatti and Marcolla 2004;Queck et al 2012). …”

Section: Models Of Mean Canopy Drag and Traditional Estimates Of Locamentioning

confidence: 99%

“…The distributed drag force depends on the leaf area density, the velocity, and the local drag coefficient. This framework has been used in a range of modelling approaches including one-dimensional first-and second-order closure (Wilson and Shaw 1977;Katul 1998;Pinard and Wilson 2001;Poggi et al 2004a;Katul et al 2011), Reynolds-averaged Navier-Stokes (RANS; Dupont et al 2006) and large-eddy simulation (LES; Shaw and Schumann 1992;Su et al 1998;Patton et al 2003;Shaw and Patton 2003;Yue et al 2007b;Dupont and Brunet 2008;Gavrilov et al 2013;Pan et al 2014a). Turbulence statistics predicted by these models are highly sensitive to the parametrization schemes employed for the local mean and instantaneous drag coefficients.…”

Section: Introductionmentioning

confidence: 99%

“…Traditionally, the mean drag coefficients are estimated using vertically distributed single-point measurements of instantaneous velocity time series (e.g., Pinard and Wilson 2001). This traditional approach assumes that data are representative of spatially-averaged metrics of statistically stationary flow within and above a horizontally homogeneous canopy.…”

Section: Introductionmentioning

confidence: 99%

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Estimating the Instantaneous Drag–Wind Relationship for a Horizontally Homogeneous Canopy

Pan

Chamecki

Nepf

2016

Boundary-Layer Meteorol

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The mean drag-wind relationship is usually investigated assuming that field data are representative of spatially-averaged metrics of statistically stationary flow within and above a horizontally homogeneous canopy. Even if these conditions are satisfied, large-eddy simulation (LES) data suggest two major issues in the analysis of observational data. Firstly, the streamwise mean pressure gradient is usually neglected in the analysis of data from terrestrial canopies, which compromises the estimates of mean canopy drag and provides misleading information for the dependence of local mean drag coefficients on local velocity scales. Secondly, no standard approach has been proposed to investigate the instantaneous drag-wind relationship, a critical component of canopy representation in LES. Here, a practical approach is proposed to fit the streamwise mean pressure gradient using observed profiles of the mean vertical momentum flux within the canopy. Inclusion of the fitted mean pressure gradient enables reliable estimates of the mean drag-wind relationship. LES data show that a local mean drag coefficient that characterizes the relationship between mean canopy drag and the velocity scale associated with total kinetic energy can be used to identify the dependence of the local instantaneous drag coefficient on instantaneous velocity. Iterative approaches are proposed to fit specific models of velocity-dependent instantaneous drag coefficients that represent the effects of viscous drag and the reconfiguration of flexible canopy elements. LES data are used to verify the assumptions and algorithms employed by these new approaches. The relationship between mean canopy drag and mean velocity, which is needed in models based on the Reynolds-averaged Navier-Stokes equations, is parametrized to account for both the dependence on velocity and the contribution from velocity variances. Finally, velocity-dependent drag coefficients lead to significant variations of the calculated displacement height and roughness length with wind speed. B Marcelo Chamecki

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Section: Models Of Mean Canopy Drag and Traditional Estimates Of Locamentioning

confidence: 99%

Section: Models Of Mean Canopy Drag and Traditional Estimates Of Locamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Estimating the Instantaneous Drag–Wind Relationship for a Horizontally Homogeneous Canopy

Pan

Chamecki

Nepf

2016

Boundary-Layer Meteorol

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“…There are many challenges to face when pursuing this goal. First, the mixing-length theory and K theory that are widely used as closure approaches to momentum equations (Wilson et al, 1998;Pinard and Wilson, 2001;Ross and Vosper, 2005;Katul et al, 2006) have been shown to have questionable validity within a forest canopy layer both theoretically (Yi, 2008) and observationally (Denmead and Bradley, 1985). Second, the analytical model (Finnigan and Belcher, 2004) is limited to neutral condition and hills of gentle slope.…”

Section: Xu Et Al: Stably Stratified Canopy Flow In Complex Terrainmentioning

confidence: 99%

Stably stratified canopy flow in complex terrain

Kutter

2015

Atmos. Chem. Phys.

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Abstract. Stably stratified canopy flow in complex terrain has been considered a difficult condition for measuring net ecosystem-atmosphere exchanges of carbon, water vapor, and energy. A long-standing advection error in eddy-flux measurements is caused by stably stratified canopy flow. Such a condition with strong thermal gradient and less turbulent air is also difficult for modeling. To understand the challenging atmospheric condition for eddy-flux measurements, we use the renormalized group (RNG) k-ε turbulence model to investigate the main characteristics of stably stratified canopy flows in complex terrain. In this twodimensional simulation, we imposed persistent constant heat flux at ground surface and linearly increasing cooling rate in the upper-canopy layer, vertically varying dissipative force from canopy drag elements, buoyancy forcing induced from thermal stratification and the hill terrain. These strong boundary effects keep nonlinearity in the two-dimensional NavierStokes equations high enough to generate turbulent behavior. The fundamental characteristics of nighttime canopy flow over complex terrain measured by the small number of available multi-tower advection experiments can be reproduced by this numerical simulation, such as (1) unstable layer in the canopy and super-stable layers associated with flow decoupling in deep canopy and near the top of canopy; (2) sub-canopy drainage flow and drainage flow near the top of canopy in calm night; (3) upward momentum transfer in canopy, downward heat transfer in upper canopy and upward heat transfer in deep canopy; and (4) large buoyancy suppression and weak shear production in strong stability.

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Cover Picture: Total Synthesis of Palau’amine (Angew. Chem. Int. Ed. 6/2010)

Seiple

Lewis

et al. 2010

Angew Chem Int Ed

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First- and Second-Order Closure Models for Wind in a Plant Canopy

Cited by 57 publications

References 7 publications

Estimating the Instantaneous Drag–Wind Relationship for a Horizontally Homogeneous Canopy

Estimating the Instantaneous Drag–Wind Relationship for a Horizontally Homogeneous Canopy

Stably stratified canopy flow in complex terrain

Cover Picture: Total Synthesis of Palau’amine (Angew. Chem. Int. Ed. 6/2010)

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