Exchange flow between a canopy and open water

Jamali, Mirmosadegh; Zhang, Xueyan; Nepf, Heidi

doi:10.1017/s0022112008002796

Cited by 21 publications

(21 citation statements)

References 35 publications

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“…Any crop-driven variation in water column density structure generates baroclinic flows (Jamali et al 2008), which, to first order, propagate at a baroclinic long wave speed NH (H = total water depth). Typical estimates for this speed are ~0.1 m s −1…”

Section: Effect Of Farm Heterogeneitymentioning

confidence: 99%

“…However, transport processes are influenced by turbulent mixing, stratification (Plew et al 2006) and canopy structure (e.g. Jamali et al 2008, Delaux et al 2011) and so analyses must extend beyond the assumptions that the canopy is hydrodynamically invisible or that the water column is homogenous. This exploratory study considers the influence of stratification and turbulent mixing on the overall productivity of a shellfish canopy.…”

Section: Introductionmentioning

confidence: 99%

“…Considering the marine environment, flow-canopy interactions of relevance to shellfish canopies include flow distortion (Gaylord et al 2007), edge effects (e.g. Ghisalberti 2009), patchiness (Song et al 1997, Folkard 2011, tidal modulation of canopy density (Stevens et al 2003), within-canopy transport (Jackson & Winant 1983) and interaction with stratification (Jackson 1984, Plew et al 2006, Jamali et al 2008. Much of this knowledge can be directly utilized in order to improve shellfish aquaculture production.…”

Section: Introductionmentioning

confidence: 99%

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Turbulent, stratified flow through a suspended shellfish canopy: implications for mussel farm design

Stevens¹,

Petersen²

2011

Aquacult. Environ. Interact.

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Observations were used to quantify the influences of turbulent flow and mixing through the suspended canopy formed by a shellfish aquaculture farm in the microtidal Danish Limfjorden. Observations included current meter/profiler timeseries data and turbulence microstructure profiling. The influence was 2-way in that the turbulence is partially driven by the canopy and in turn the canopy is affected by the turbulence. The canopy reduced the flow speeds within its interior, which was sufficient to reduce levels of turbulent kinetic energy so that withincanopy rates of turbulent kinetic energy dissipation ε were between 10 −8 and 5 × 10 −6 m 2 s −3. Stratification and turbulence were generally inter-related. It was difficult to link the canopy effect to changes in stratification. This was partly due to a high degree of natural variability and partly because the canopy did not appear to generate that much mixing relative to background variability. Vertical diffusivities enabled estimates of the effect of mixing on nutrient depletion and suggest that in the investigated farm set-up vertical diffusivities are secondary in terms of contribution to this relationship but that they could play a dominant role in farms with a more spacious or compressed set-up of canopies. However, vertical flux estimates imply that there must be transverse fluxes of material. Results suggest several avenues for enhanced sustainable shellfish production. For example, canopy flushing can be enhanced with suitable arrangement of crop within a farmed area (heterogeneity). In addition, stratification persists within the canopy and so exposure to nutrient-deplete water can be minimized through staggered crop heights. However, to benefit from this knowledge, improved understanding of long-term variability in the background environment is required.

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Section: Effect Of Farm Heterogeneitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Turbulent, stratified flow through a suspended shellfish canopy: implications for mussel farm design

Stevens¹,

Petersen²

2011

Aquacult. Environ. Interact.

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“…The stream function ψ(u = − 1 [26]) is used to eliminate the pressure term in Eqs. (2) and (3) and yield the non-dimensional streamfunction equation:…”

Section: Scaling Analysismentioning

confidence: 99%

Wind effect on diurnal thermally driven flow in vegetated nearshore of a lake

Lin

2014

Environ Fluid Mech

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In this study, a highly idealized model is developed to discuss the interplay of diurnal heating/cooling induced buoyancy and wind stress on thermally driven flow over a vegetated slope. Since the model is linear, the horizontal velocity can be broken into buoyancy-driven and surface wind-driven parts. Due to the presence of rooted vegetation, the circulation strength even under the surface wind condition is still significantly reduced, and the transient (adjustment) stage for the initial conditions is shorter than that without vegetation because of the reduced inertia. The flow in shallows is dominated by a viscosity/buoyancy balance as the case without wind, while the effect of wind stress is limited to the upper layer in deep water. In the lower layer of deep regions, vegetative drag is prevailing except the near bottom regions where viscosity dominates. Under the unidirectional wind condition, a critical dimensionless shear stress cri to stop the induced flow can be found and is a function of the horizontal location x. For the periodic wind condition, if the two forcing mechanisms work in concert (θ = 0), the circulation magnitude can be increased. For the case where buoyancy and wind shear stress act against each other (θ = 1 2 ), the circulation strength is reduced and its structure becomes more complex. However, the flow magnitudes near the bottom for θ = 0 and θ = 1 2 are comparable because surface wind almost has no influence.

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“…Temperature differences are usually small in the littoral zone, and the Boussinesq approximation on water density variations can be adopted. The vegetative drag following a quadratic drag law can be represented as [21,22] …”

Section: Mathematical Formulationmentioning

confidence: 99%

Effects of a sharp change of emergent vegetation distributions on thermally driven flow over a slope

Lin

2014

Environ Fluid Mech

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In this study, thermally driven flow within a sharp change of rooted emergent vegetation distributions is discussed. A conceptual and linear model is developed to study the interferences and competitions between two forcing mechanisms (vegetation shading and sloping bottom effects) on circulation patterns. The two forcing mechanisms can counteract or reinforce each other according to the presence of emergent vegetation in shallow or deep regions. For tall vegetation in shallows and open water in deep regions, vegetation shading leads to opposite temperature gradients against those from a slope. A critical vegetation blockage B critical is found to cause a minimum horizontal exchange flowrate and divide the flow regime as topographic or vegetation shading dominated. In clear water, opposite circulation from the bottom is produced and gradually spreads to the whole water column. On the contrary, in turbid water, the opposite circulation emerges from the water surface and gradually propagates to the sloping bottom. The circulation in turbid water is more easily affected by a sharp change of vegetation distributions rather than clear water. For open in shallows and tall vegetation in deep water, pressure gradients from vegetation shading can enhance buoyancy from the sloping bottom and lead to greater horizontal exchange flowrates. Due to a sharp change of emergent vegetation distributions, horizontal exchange flowrates are possibly increased and greater than those without vegetation. In short, circulation patterns and strength can be significantly affected by a sharp change of emergent vegetation distributions.

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Exchange flow between a canopy and open water

Cited by 21 publications

References 35 publications

Turbulent, stratified flow through a suspended shellfish canopy: implications for mussel farm design

Turbulent, stratified flow through a suspended shellfish canopy: implications for mussel farm design

Wind effect on diurnal thermally driven flow in vegetated nearshore of a lake

Effects of a sharp change of emergent vegetation distributions on thermally driven flow over a slope

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