On the total entrained flow rate of artificial downwelling

Xiao, Canbo; Fan, Wei; Yao, Zhongzhi; Qiang, Yongfa; Pan, Yiwen; Chen, Ying

doi:10.1016/j.oceaneng.2019.04.014

Cited by 10 publications

(8 citation statements)

References 33 publications

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“…Overall, AD outperforms AU in mid-depth oxygenation. The mentioned strengthened pycnocline mixing during AD has been suggested by some nearfield studies (Stigebrandt et al, 2015;Xiao et al, 2019). In their field experiment in By Fjord, Stigebrandt et al (2015) found that below-pycnocline mixing is intensified by the plume-like compensatory upwelling at a scale of several kilometers.…”

Section: Mechanismmentioning

confidence: 72%

“…AD simulations using the pipe length of 160, 285, 440, and 625 m suggest oxygen-deficit water increased by 25, 11, 4, and 24%, respectively. Hypoxic water growing more slowly with increasing pipe length except for 625 m simulation is a consequence of longer pipes closer to the core region of low-oxygen water, which is estimated deeper than 400 m. Compared to 440 m pipe, 625 m pipe instead suggests a greater expansion of oxygen-deficit water, likely due to less pycnocline mixing enhancement with deeper discharge (Xiao et al, 2019). The optimal discharging depth thus is where oxygen content reaches sufficiently low to necessitate oxygenation and as close as possible to the pycnocline depth.…”

Section: Mechanismmentioning

confidence: 91%

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Could Artificial Downwelling/Upwelling Mitigate Oceanic Deoxygenation in Western Subarctic North Pacific?

et al. 2021

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Subpolar gyre regions such as the Western Subarctic North Pacific (WSNP) contain sluggish, low-oxygen water, and are threatened by loss of oxygen (deoxygenation). Our simulations under RCP 8.5 emission scenario suggest that installing pipes to induce artificial downwelling and upwelling (AD and AU) provides short-term solutions to combat deoxygenation in the WSNP. With no engineering, the WSNP's subsurface oxygen decreases by 30–100 mmol/m3 by the year 2100. Continuous implementation of AD and AU instead counters this declining trend, and AD is more effective than AU. The oxygenation effect is primarily a consequence of how the two engineering schemes vertically redistribute oxygen via physical processes. AD directly improves oxygen at depth via advecting surface water toward the ocean interior and subsequent enhanced pycnocline mixing, and AU does so via generating compensatory downwelling outside of the pipes. Both schemes take near 40 years to complete the oxygenation. After that, oxygen reaches a new equilibrium state in the WSNP with no further improvement by the engineering. AD and AU both strongly increase primary production surrounding the deployment sites, but lead only to weak enhancement of aerobic respiration in subsurface water and thus a minor impact on the oxygenation. Other unwanted environmental side effects are negligible compared to those caused by rapid climate change within this century, including outgassing of carbon dioxide, pH decrease, and precipitation reduction.

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Section: Mechanismmentioning

confidence: 72%

Section: Mechanismmentioning

confidence: 91%

Could Artificial Downwelling/Upwelling Mitigate Oceanic Deoxygenation in Western Subarctic North Pacific?

et al. 2021

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“…The plume in the steady state is divided into two regions according to the type of leading forces exerted on the plume. In the interaction region [62], the initial jet interacts with the reverse main flow, where the entrainment dynamics are governed by momentum flux and buoyancy flux [64]. The results of the numerical studies showed that the ratio of the terminal total entrained flow rate to the initial jet flow rate first decreased as either the initial jet velocity or the relative density difference became larger, but then increased.…”

Section: Overview Of Numerical Studies For Artificial Downwellingmentioning

confidence: 99%

“…Xiao et al (2019) focused on the total entrained (TE) flow rate of artificial downwelling representing the magnitude of entrainment transport [62]. A verified standard k-ε turbulence model, in which different initial pipe flow speeds, density differences, and pipe radii were involved, was applied to characterize the hydrodynamic performance of the injection of a negatively buoyant jet from a round pipe into a stagnant, homogeneous ambient medium [63].…”

Section: Overview Of Numerical Studies For Artificial Downwellingmentioning

confidence: 99%

Review of Artificial Downwelling for Mitigating Hypoxia in Coastal Waters

Liu

Zhao

Xiao

et al. 2020

Water

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Hypoxia is becoming a serious problem in coastal waters in many parts of the world. Artificial downwelling, which is one of the geoengineering-based adaptation options, was suggested as an effective means of mitigating hypoxia in coastal waters. Artificial downwelling powered by green energy, such as solar, wind, wave, or tidal energy, can develop a compensatory downward flow on a kilometer scale, which favors below-pycnocline ventilation and thus mitigates hypoxia in bottom water. In this paper, we review and assess the technical, numerical, and experimental aspects of artificial downwelling all over the world, as well as its potential environmental effects. Some basic principles are presented, and assessment and advice are provided for each category. Some suggestions for further field-based research on artificial downwelling, especially for long-term field research, are also given.

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“…One would expect as much entrainment as it could be, otherwise, a great portion of dissolved oxygen comes back to the surface, which is unsatisfactory. The authors have published one paper on this issue and claim that the ratio between the total entrained flow rate and the source discharge depends on the ambient current speed, the relative density difference and the pump geometry [26]. For the scenario of Muping marine ranch, assuming a constant ratio between the pipe length immersed below the pycnocline and the pipe diameter, incident current speed is relatively small and indicative of a high entrainment ratio [26].…”

Section: Effects Of Tube Geometrical Dimensions On Downwelling Flow Rmentioning

confidence: 99%

Experimental Study on the Performance of an Innovative Tide-Induced Device for Artificial Downwelling

et al. 2019

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Hypoxia has been increasingly observed in estuaries and coastal marine ecosystems around the world. In this paper, a tide-powered artificial downwelling device is proposed to potentially alleviate hypoxia in bottom waters. The downwelling device mainly consists of a vertical square tube, a 90° bend sitting on the top of the tube, two symmetrical-guide plates which installed alongside the vertical tube, a static mixer, and an artificial reef. Scale model experiments are performed with respect to different density difference heads, horizontal current velocities, and tube geometries. The results show that the downwelling flow rate is dependent on horizontal current velocity, tube geometry parameters, and the density profile of ambient water. In addition, increasing the equivalent diameter and bend radius of the device can decrease the total loss coefficient in the tube, which in turns enhance the downwelling efficiency. The two symmetrical-guide plates also generate obvious downwelling of surface water which further improves the whole performance of the device. Further work will need to determine the influence of the other parts of the device, such as the static mixer and artificial reef, on the downwelling efficiency.

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On the total entrained flow rate of artificial downwelling

Cited by 10 publications

References 33 publications

Could Artificial Downwelling/Upwelling Mitigate Oceanic Deoxygenation in Western Subarctic North Pacific?

Could Artificial Downwelling/Upwelling Mitigate Oceanic Deoxygenation in Western Subarctic North Pacific?

Review of Artificial Downwelling for Mitigating Hypoxia in Coastal Waters

Experimental Study on the Performance of an Innovative Tide-Induced Device for Artificial Downwelling

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