Shallow Flows Over a Permeable Medium: The Hydrodynamics of Submerged Aquatic Canopies

Ghisalberti, Marco; Nepf, Heidi

doi:10.1007/s11242-008-9305-x

Cited by 97 publications

(100 citation statements)

References 34 publications

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“…Gambi et al1990, Ghisalberti & Nepf 2009). This occurred primarily because the unidirectional flow in the flume was characteristic of the tidally driven flows that dominated the field site.…”

Section: Discussionmentioning

confidence: 99%

Effects of a small-bladed macroalgal canopy on benthic boundary layer dynamics: implications for nutrient transport

Kregting¹,

Stevens²,

Cornelisen³

et al. 2011

Aquat. Biol.

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Field and laboratory velocity profiles were used to quantify boundary layer dynamics within communities of a small (< 0.2 m tall), dense canopy-forming seaweed Adamsiella chauvinii (Rhodophyta) in a soft-sediment habitat and to examine the role of hydrodynamics in modulating nutrient supply. At the 'canopy scale' there was a mixing layer at the fluid−canopy interface where turbulent kinetic energy was greatest, potentially enhancing nutrient uptake in this region. In the lower half of the canopy, a drag-dominated area of very low water velocity (< 0.01 m s −1 ) occurred. Spectral analysis revealed a reduction in energy within the canopy of around 1 Hz. The hydrodynamic parameters obtained from flume measurements were in good agreement with those recorded in the field. To understand the implications of the hydrodynamic environment on nutrient uptake, a flushing ratio was developed that compares the time for macroalgae to remove all nutrients from the canopy volume relative to the timescale for flushing. Results suggest that when nutrient demand is low, the canopy is well flushed and not mass-transfer limited. However when nutrient demand is high, the canopy can deplete nutrients more quickly than they can be replenished by ambient flows and are potentially mass-transfer limited.

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Section: Discussionmentioning

confidence: 99%

Effects of a small-bladed macroalgal canopy on benthic boundary layer dynamics: implications for nutrient transport

Kregting¹,

Stevens²,

Cornelisen³

et al. 2011

Aquat. Biol.

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“…[30] An estimate of the transition length L T required for the flow encountering the patch to reach a new equilibrium state was also calculated, following Ghisalberti and Nepf [2009]:…”

Section: Bulk Drag Parametersmentioning

confidence: 99%

Plant patch hydrodynamics in streams: Mean flow, turbulence, and drag forces

Siniscalchi¹,

Nikora²,

Aberle³

2012

Water Resources Research

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[1] This paper investigates the effects of a finite-size vegetation patch on flow turbulence, variations in drag forces experienced by individual plants within the patch, and flow-drag interrelations. The experiments were conducted in a 32 m long laboratory flume with a 2.8 m long artificial patch. The plants were arranged to form a staggered pattern and three flow scenarios were tested. Velocities were recorded with an acoustic doppler velocimeter, whereas specifically designed devices were used to simultaneously measure the drag forces acting on nine plants within the patch. For all studied cases, the results show zones of increased turbulent energy close to the leading edge and along the patch canopy top, where turbulence shear production is enhanced. Zones of negative Reynolds stresses Àu 0 w 0 are found inside the patch and they reflect the influence of plant morphology, which affects the shape of the longitudinal velocity profile and associated turbulent fluxes. Modifications to the power spectral densities of velocity by the plants indicate the emergence of two plantinduced mechanisms of energy production, which are most likely related to the wake turbulence and shear layer turbulence. Drag fluctuations appear to be correlated with the velocity field, with this correlation being especially profound at the highest-studied flow rate. The data suggest that the highlighted correlation stems from flow-plant interactions at the top of the vegetation canopy, likely due to the presence of large three-dimensional coherent structures.

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“…Vertical transport in the wake zone is governed by the hydraulic gradient and balances between bed and canopy drag (Ghisalberti and Nepf, 2009). Vertical transport in the exchange zone is governed by the hydraulic gradient and turbulent stresses (Nepf and Vivoni, 2000).…”

Section: Submerged Aquatic Vegetationmentioning

confidence: 99%

A fluid-mechanics based classification scheme for surface transient storage in riverine environments: quantitatively separating surface from hyporheic transient storage

Jackson

Haggerty

Apte

2013

Hydrol. Earth Syst. Sci.

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Abstract. Surface transient storage (STS) and hyporheic transient storage (HTS) have functional significance in stream ecology and hydrology. Currently, tracer techniques couple STS and HTS effects on stream nutrient cycling; however, STS resides in localized areas of the surface stream and HTS resides in the hyporheic zone. These contrasting environments result in different storage and exchange mechanisms with the surface stream, which can yield contrasting results when comparing transient storage effects among morphologically diverse streams. We propose a fluid mechanics approach to quantitatively separate STS from HTS that involves classifying and studying different types of STS. As a starting point, a classification scheme is needed. This paper introduces a classification scheme that categorizes different STS in riverine systems based on their flow structure. Eight STS types are identified and some are subcategorized based on characteristic mean flow structure: (1) lateral cavities (emergent and submerged); (2) protruding in-channel flow obstructions (backward-and forward-facing step); (3) isolated in-channel flow obstructions (emergent and submerged); (4) cascades and riffles; (5) aquatic vegetation (emergent and submerged); (6) pools (vertically submerged cavity, closed cavity, and recirculating reservoir); (7) meander bends; and (8) confluence of streams. The long-term goal is to use the classification scheme presented to develop predictive mean residence times for different STS using fieldmeasurable hydromorphic parameters and obtain an effective STS mean residence time. The effective STS mean residence time can then be deconvolved from the transient storage residence time distribution (measured from a tracer test) to obtain an estimate of HTS mean residence time.

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Shallow Flows Over a Permeable Medium: The Hydrodynamics of Submerged Aquatic Canopies

Cited by 97 publications

References 34 publications

Effects of a small-bladed macroalgal canopy on benthic boundary layer dynamics: implications for nutrient transport

Effects of a small-bladed macroalgal canopy on benthic boundary layer dynamics: implications for nutrient transport

Plant patch hydrodynamics in streams: Mean flow, turbulence, and drag forces

A fluid-mechanics based classification scheme for surface transient storage in riverine environments: quantitatively separating surface from hyporheic transient storage

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