Reduced Mixing in a Marine Macrophyte Canopy

Ackerman, Josef Daniel; Ōkubo, Akira

doi:10.2307/2390209

Cited by 206 publications

(147 citation statements)

References 27 publications

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“…These are erect, gently swaying, honami/monami (coherently waving) and prone [6,18,41,42]. The regime of motion observed for a particular canopy will be determined by the biomechanical properties of the vegetation as well as the drag force [32,43].…”

Section: Plant Response and Interaction With The Flowmentioning

confidence: 99%

“…As research into aquatic vegetation canopies has subsequently developed, this theory has been transferred and applied to aquatic environments with much of the terminology associated with terrestrial canopy flows being adopted and adapted for aquatic canopy flows [7,18]. However, aquatic canopies inhabit very different physical environments to terrestrial canopies.…”

Section: Introductionmentioning

confidence: 99%

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Does the canopy mixing layer model apply to highly flexible aquatic vegetation? Insights from numerical modelling

et al. 2016

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Vegetation is a characteristic feature of shallow aquatic flows such as rivers, lakes and coastal waters. Flow through and above aquatic vegetation canopies is commonly described using a canopy mixing layer analogy which provides a canonical framework for assessing key hydraulic characteristics such as velocity profiles, large-scale coherent turbulent structures and mixing and transport processes for solutes and sediments. This theory is well developed for the case of semi-rigid terrestrial vegetation and has more recently been applied to the case of aquatic vegetation. However, aquatic vegetation often displays key differences in morphology and biomechanics to terrestrial vegetation due to the different environment it inhabits. Here we investigate the effect of plant morphology and biomechanical properties on flow-vegetation interactions through the application of a coupled LES-biomechanical model. We present results from two simulations of aquatic vegetated flows: one assuming a semi-rigid canopy and the other a highly flexible canopy and provide a comparison of the associated flow regimes. Our results show that while both cases display canopy mixing layers, there are also clear differences in the shear layer characteristics and turbulent processes between the two, suggesting that the semi-rigid approximation may not provide a complete representation of flow-vegetation interactions.

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Section: Plant Response and Interaction With The Flowmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Does the canopy mixing layer model apply to highly flexible aquatic vegetation? Insights from numerical modelling

et al. 2016

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“…Extreme pronation will eliminate vertical exchange entirely by creating by a solid leaf barrier at the top of the canopy. In some flexible canopies, moderate, unidirectional flows produce coherent waving called "monami" [Ackerman and Okubo, 1993]. Preliminary laboratory studies suggest that vertical exchange i s enhanced during monami events [Ghisalberti, 2000].…”

Section: Summary and Extension To Other Canopiesmentioning

confidence: 99%

Flow structure in depth‐limited, vegetated flow

Nepf¹,

Vivoni²

2000

J. Geophys. Res.

705

621

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Abstract. Aquatic vegetation controls the mean and turbulent flow structure in channels and coastal regions and thus impacts the fate and transport of sediment and contaminants.Experiments in an open-channel flume with model vegetation were used to better understand how vegetation impacts flow. In particular, this study describes the transition between submerged and emergent regimes based on three aspects of canopy flow: mean momentum, turbulence, ard exchange dynamics. The observations suggest that flow within an aquatic canopy may be divided into two regions. In the upper canopy, called the "vertical exchange zone", vertical turbulent exchange with the overlying water is dynamically significant to the momentum balance and turbulence; and turbulence produced by mean shear at the top of the canopy is important. The lower canopy is called the "longitudinal exchange zone" because it communicates with surrounding water predominantly through longitudinal advection. In this region turbulence is generated locally by the canopy elements, and the momentum budget is a simple balance of vegetative drag and pressure gradient. In emergent canopies, only a longitudinal exchange zone is present. When the canopy becomes submerged, a vertical exchange zone appears at the top of the canopy and deepens into the canopy as the depth of submergence increases.

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“…The use of the term ''canopy'' reflects the similarity these flows have to atmospheric flows over terrestrial canopies (Finnigan 2000). What distinguishes canopy flow models most from conventional boundary layer models are that (1) they describe the flow within the roughness elements, and (2) they include an inflection point in the mean velocity profile that leads to the generation of instabilities that enhance turbulent exchange between the canopy and the overlying water column (Ackerman and Okubo 1993;Ghisalberti and Nepf 2002).…”

mentioning

confidence: 99%

Modeling flow in coral communities with and without waves: A synthesis of porous media and canopy flow approaches

Lowe

Shavit

Falter

et al. 2008

Limnology & Oceanography

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Both canopy flow and porous media theories have been developed independent of one another to predict flow through submerged porous structures. These approaches are very similar, albeit with some key differences in how canopy resistance forces are parameterized. Canopy models provide a means of parameterizing the shear stresses that occur at the top of the canopy, whereas porous media models can often provide a simpler and more tractable way of parameterizing turbulent form drag based on simple morphological metrics and empirical relationships already in the hydrology literature. We developed a set of equations combining aspects of both models and applied this hybridized model to predict the flow structure within an experimental canopy formed by the branching coral Porites compressa, using model parameter values obtained from the literature. Results from the model predictions agreed well with direct measurements of flow speed and flow forces derived from particle image velocimetry under conditions of both unidirectional and wave-driven oscillatory flow.

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Reduced Mixing in a Marine Macrophyte Canopy

Cited by 206 publications

References 27 publications

Does the canopy mixing layer model apply to highly flexible aquatic vegetation? Insights from numerical modelling

Does the canopy mixing layer model apply to highly flexible aquatic vegetation? Insights from numerical modelling

Flow structure in depth‐limited, vegetated flow

Modeling flow in coral communities with and without waves: A synthesis of porous media and canopy flow approaches

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