The impact of macroalgae on mean and turbulent flow fields

Thomas, Robert E.; McLelland, Stuart J.

doi:10.1016/s1001-6058(15)60500-5

Cited by 12 publications

(9 citation statements)

References 32 publications

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“…Postprocessing of the aDv data followed the recommendation of Thomas and McLelland []. Initially, two‐dimensional phase unwrapping or dealiasing was undertaken applying the two‐step noncontinuous quality‐guided path (TSNCQUAL) algorithm [ Parkhurst et al ., ].…”

Section: Methodsmentioning

confidence: 99%

Modeling complex flow structures and drag around a submerged plant of varied posture

Boothroyd

Hardy

Warburton

et al. 2017

Water Resources Research

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Although vegetation is present in many rivers, the bulk of past work concerned with modeling the influence of vegetation on flow has considered vegetation to be morphologically simple and has generally neglected the complexity of natural plants. Here we report on a combined flume and numerical model experiment which incorporates time‐averaged plant posture, collected through terrestrial laser scanning, into a computational fluid dynamics model to predict flow around a submerged riparian plant. For three depth‐limited flow conditions (Reynolds number = 65,000–110,000), plant dynamics were recorded through high‐definition video imagery, and the numerical model was validated against flow velocities collected with an acoustic Doppler velocimeter. The plant morphology shows an 18% reduction in plant height and a 14% increase in plant length, compressing and reducing the volumetric canopy morphology as the Reynolds number increases. Plant shear layer turbulence is dominated by Kelvin‐Helmholtz type vortices generated through shear instability, the frequency of which is estimated to be between 0.20 and 0.30 Hz, increasing with Reynolds number. These results demonstrate the significant effect that the complex morphology of natural plants has on in‐stream drag, and allow a physically determined, species‐dependent drag coefficient to be calculated. Given the importance of vegetation in river corridor management, the approach developed here demonstrates the necessity to account for plant motion when calculating vegetative resistance.

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Section: Methodsmentioning

confidence: 99%

Modeling complex flow structures and drag around a submerged plant of varied posture

Boothroyd

Hardy

Warburton

et al. 2017

Water Resources Research

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“…Besides the CDR effect of MOS, in case of large scale deployment, the macroalgae farms are likely to increase the albedo of the oceans's surface, especially when they occur near the sea surface (Fogarty et al, 2018;Bach et al, 2021). Meanwhile, we have not considered possible hydrodynamic impacts on ocean circulation, as the thick macroalgae layers and the farming infrastructures may influence the momentum and mixing of the ambient flow fields (Liu and Huguenard, 2020;Nepf, 2012;Thomas and McLelland, 2015).…”

Section: Leakage Of Mos Sequestered Carbonmentioning

confidence: 99%

Carbon Dioxide Removal via Macroalgae Open-ocean Mariculture and Sinking: An Earth System Modeling Study

Keller

Oschlies

2022

Preprint

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Abstract. In this study we investigate open-ocean macroalgae mariculture and sinking (MOS) as ocean-based carbon dioxide removal (CDR) method. Embedding a macroalgae model into an Earth system model, we simulate macroalgae mariculture in the open-ocean surface layer followed by fast sinking of the carbon-rich macroalgal biomass to the deep seafloor (depth > 3,000 m). We also test the combination of MOS with artificial upwelling (AU), which fertilizes the macroalgae by pumping nutrient-rich deeper water to the surface. The simulations are done under RCP4.5 a moderate emission pathway. When deployed globally between years 2020 and 2100, the simulated CDR potential of MOS is 270 PgC, which is further boosted by AU to 447 PgC. More than half of MOS-sequestered carbon retains in the ocean after cessation at year 2100 until year 3000. The major side effect of MOS on pelagic ecosystems is the reduction of phytoplankton net primary production (PNPP) due to the nutrient competition and canopy shading by macroalgae. MOS shrinks the mid layer oxygen minimum zones (OMZs) by reducing the organic matter export to, and remineralization in, subsurface and intermediate waters, while it creates new OMZs on the seafloor by oxygen consumption from remineralization of sunken biomass. MOS also impacts the global carbon cycle, reduces the atmospheric and terrestrial carbon reservoir when enhancing the ocean carbon reservoir. MOS also enriches the dissolved inorganic carbon in the deep ocean. Effects are mostly reversible after cessation of MOS, though recovery is not complete by year 3000. In a sensitivity experiment without remineralization of sunk MOS biomass, the entire MOS-captured carbon is permanently stored in the ocean, but the lack of remineralized nutrients causes a long-term nutrient decline in the surface layers and thus reduces PNPP. Our results suggest that MOS has a considerable potential as an ocean-based CDR method. However, MOS has inherent side effects on marine ecosystems and biogeochemistry, which will require a careful evaluation beyond this first idealized modeling study.

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“…The acoustic Doppler velocimeter (ADV) has been widely used in both laboratory and field settings for the measurement of flow velocity [1,3,6]. ADV is based on based on the Doppler effect and can accurately measure the mean velocities and turbulent statistical parameters [7], especially the flow characteristics under the influence of aquatic plants [1,3].…”

Section: Introductionmentioning

confidence: 99%

Effect of the Number of Leaves in Submerged Aquatic Plants on Stream Flow Dynamics

Yan

Tian

Lei

et al. 2019

Water

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The main purpose of this study is to investigate the effects of aquatic plants with no leaves (L0), 4 leaves (L4), 8 leaves (L8), and 12 leaves (L12) on the mean streamwise velocity, turbulence structure, and Manning's roughness coefficient. The results show that the resistance of submerged aquatic plants to flow velocity is discontinuous between the lower aquatic plant layer and the upper free water layer. This leads to the difference of flow velocity between the upper and lower layers. An increase of the number of leaves leads to an increase in the flow velocity gradient in the upper non-vegetation area and a decrease in the flow velocity in the lower vegetation area. In addition, aquatic plants induce a momentum exchange near the top of the plant and increase the Reynold's stress and turbulent kinetic energy. However, because of the inhibition of leaf area on the momentum exchange, the Reynold's stress and turbulent kinetic energy increase first and then decrease with the increase in the number of leaves. Quadrant analysis shows that ejection and sweep play a dominant role in momentum exchange. Aquatic plants can also increase the Reynold's stress by increasing the ejection and sweep. The Manning's roughness coefficient increases with the increasing number of leaves.

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The impact of macroalgae on mean and turbulent flow fields

Cited by 12 publications

References 32 publications

Modeling complex flow structures and drag around a submerged plant of varied posture

Modeling complex flow structures and drag around a submerged plant of varied posture

Carbon Dioxide Removal via Macroalgae Open-ocean Mariculture and Sinking: An Earth System Modeling Study

Effect of the Number of Leaves in Submerged Aquatic Plants on Stream Flow Dynamics

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