Impact of current speed on mass flux to a model flexible seagrass blade

Lei, Jiarui; Nepf, Heidi

doi:10.1002/2016jc011826

Cited by 19 publications

(11 citation statements)

References 47 publications

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“…The former inequality is a good approximation for slender vegetation with b/H 1. The latter inequality holds whenever the velocity of the fluid is small compared to the speed of sound through the beams, which is also typical for aquatic vegetation (Lei & Nepf 2016).…”

Section: Simplification and Non-dimensionalisationmentioning

confidence: 86%

Shear-induced instabilities of flows through submerged vegetation

2020

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We consider the instabilities of flows through a submerged canopy, and show how the full governing equations of the fluid-structure interactions can be reduced to a compact framework that captures many key features of vegetative flow. By modelling the canopy as a collection of homogeneous elastic beams, we predict the steady configuration of the plants in response to a unidirectional flow. This treatment couples the beam equations in the canopy to the fluid momentum equations. Our linear stability analysis suggests new insights into the development of instabilities at the surface of the vegetative region. In particular, we show that shear at the top of the canopy is a dominant factor in determining the onset of instabilities known as monami. Based on numerical and asymptotic analysis of the generalised eigenvalue problem, the system is shown to be stable if the canopy is sufficiently sparse or if the plants are sufficiently flexible.

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Section: Simplification and Non-dimensionalisationmentioning

confidence: 86%

Shear-induced instabilities of flows through submerged vegetation

2020

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“…Previous studies have suggested that Turbulent KE may influence nutrient uptake (Anderson and Charters ; Koch ), and the total energy parameter captures this influence. Specifically, when Turbulent KE is weak, flux is controlled by the time‐mean diffusive sublayer thickness, which is a function of the time‐mean velocity (e.g., Hansen et al ; Rominger and Nepf ; Lei and Nepf ). However, when the Turbulent KE is high, periodic disturbances of the diffusive sublayer by the turbulence can create instantaneously higher concentration gradients at the surface and, thus, higher flux (e.g., Stevens and Hurd ; Huang et al ; Rominger and Nepf ).…”

Section: Discussionmentioning

confidence: 99%

Turbulence‐mediated facilitation of resource uptake in patchy stream macrophytes

Cornacchia

Licci

Nepf

et al. 2018

Limnology & Oceanography

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Many landscapes are characterized by a patchy, rather than homogeneous, distribution of vegetation. Often this patchiness is composed of single‐species patches with contrasting traits, interacting with each other. To date, it is unknown whether patches of different species affect each other's uptake of resources by altering hydrodynamic conditions, and how this depends on their spatial patch configuration. Patches of two contrasting aquatic macrophyte species (i.e., dense canopy‐forming Callitriche and sparse canopy‐forming Groenlandia) were grown together in a racetrack flume and placed in different patch configurations. We measured 15NH4+ uptake rates and hydrodynamic properties along the centerline and the lateral edge of both patches. When the species with a taller, denser canopy (Callitriche) was located upstream of the shorter, sparser species (Groenlandia), it generated turbulence in its wake that enhanced nutrient uptake for the sparser Groenlandia. At the same time, Callitriche benefited from being located at a leading edge where it was exposed to higher mean velocity, as its canopy was too dense for turbulence to penetrate from upstream. Consistent with this, we found that ammonium uptake rates depended on turbulence level for the sparse Groenlandia and on mean flow velocity for the dense Callitriche, but Total Kinetic Energy was the best descriptor of uptake rates for both species. By influencing turbulence, macrophyte species interact with each other through facilitation of resource uptake. Hence, heterogeneity due to multispecific spatial patchiness has crucial implications for both species interactions and aquatic ecosystem functions, such as nitrogen retention.

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“…The dynamic response of blades to symmetric wave forcing is investigated using the cable model. Blade geometric and material properties are adopted from those summarized in Lei and Nepf (), which are also provided in Table . In this case study, the blade length

l = 0.05

–0.60 m and the flexural rigidity

E I = 0.13 \times 1 0^{- 5}

to 3.9

\times 1 0^{- 5}

N m

^{2}

are used to represent a variety of blade characteristics.…”

Section: Symmetric and Asymmetric Blade Motionsmentioning

confidence: 99%

“…Blade Geometric and Material Properties for the Selected Species Used in the Present Study FollowingLei and Nepf (2016) …”

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confidence: 99%

Mechanisms for the Asymmetric Motion of Submerged Aquatic Vegetation in Waves: A Consistent‐Mass Cable Model

et al. 2020

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Submerged aquatic vegetation (SAV) provides primary products for the food web, as well as shelter and nursery for many juvenile species. SAV can also attenuate waves, stabilize the seabed, and improve water quality. These environmental services are influenced by the dynamic motion of SAV. In this paper, a consistent‐mass cable model was developed to investigate flow interaction with a flexible vegetation blade. Compared with previous vegetation models, the cable model showed improvements in simulating blade motions in waves with and without currents, especially for “second‐normal‐mode‐like” blade motion. Wave asymmetry would cause blade motion to be asymmetric. However, asymmetric blade motion may also occur in symmetric waves. Results indicate that the asymmetric blade motion in symmetric waves is induced by two major mechanisms: (i) the spatial asymmetry of the encountered wave orbital velocities (wave motion relative to blade) due to blade displacements and (ii) the asymmetric action on the blade by vertical wave orbital velocities. Consequently, the blade motion is asymmetric even underneath symmetric waves unless (i) blade length ( l) is much smaller than the wavelength ( lfalse/L≪1), (ii) blade length is much smaller than the water depth ( lfalse/h≪1) in finite water depth waves, or (iii) water depth is much smaller than the wavelength ( hfalse/L≪1). Peak asymmetric blade motion occurs as lfalse/L increases to a critical value. The peak asymmetry increases with wave height and blade length but decreases with increasing blade flexural rigidity. Blade motion characteristics play an important role in wave‐vegetation interaction, wave‐driven currents, wave‐attenuation capacity, breakage of vegetation and ecosystem services.

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Impact of current speed on mass flux to a model flexible seagrass blade

Cited by 19 publications

References 47 publications

Shear-induced instabilities of flows through submerged vegetation

Shear-induced instabilities of flows through submerged vegetation

Turbulence‐mediated facilitation of resource uptake in patchy stream macrophytes

Mechanisms for the Asymmetric Motion of Submerged Aquatic Vegetation in Waves: A Consistent‐Mass Cable Model

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