Air-Trap-Technology: Bubble-Free Gas Transfer in Large Scale

Abstract. In the present paper a modified vorticity-based model for gas transfer under breaking waves in the absence of significant wind forcing is presented. A theoretically valid and practically applicable mathematical expression is suggested for the assessment of the oxygen transfer coefficient in the area of wave-breaking. The proposed model is based on the theory of surface renewal that expresses the oxygen transfer coefficient as a function of both the wave vorticity and the Reynolds wave number for breaking waves. Experimental data were collected in wave flumes of various scales: a) small-scale experiments were carried out using both a sloping beach and a rubble-mound breakwater in the wave flume of the Laboratory of Harbor Works, NTUA, Greece; b) large-scale experiments were carried out with a sloping beach in the wind-wave flume of Delft Hydraulics, the Netherlands, and with a three-layer rubble mound breakwater in the Schneideberg Wave Flume of the Franzius Institute, University of Hannover, Germany. The experimental data acquired from both the small- and large-scale experiments were in good agreement with the proposed model. Although the apparent transfer coefficients from the large-scale experiments were lower than those determined from the small-scale experiments, the actual oxygen transfer coefficients, as calculated using a discretized form of the transport equation, are in the same order of magnitude for both the small- and large-scale experiments. The validity of the proposed model is compared to experimental results from other researchers. Although the results are encouraging, additional research is needed, to incorporate the influence of bubble mediated gas exchange, before these results are used for an environmental friendly design of harbor works, or for projects involving waste disposal at sea.

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Planning a drilling campaign in a petroleum province using high resolution 3D seismic data – IODP proposal 909

10.5194/egusphere-egu2020-20571 ◽

2020 ◽

Author(s):

David Cox ◽

Andrew M. W. Newton ◽

Paul C. Knutz ◽

Mads Huuse

Keyword(s):

High Resolution ◽

Gas Hydrate ◽

Seismic Data ◽

Large Scale ◽

Greenland Ice Sheet ◽

Hydrocarbon Exploration ◽

3D Seismic ◽

Free Gas ◽

Shallow Subsurface ◽

3D Seismic Data

A drilling hazard assessment has been completed for a large area of the NW Greenland-Baffin Bay continental shelf. This assessment was in relation to International Ocean Discovery Program (IODP) proposal 909 that aims to drill several sites across the shelf in an attempt to better understand the evolution and variability of the northern Greenland Ice Sheet. The assessment utilised high quality and extensive 3D seismic data that were acquired during recent hydrocarbon exploration interest in the area &#8211; a fact that highlights the risk of drilling in a petroleum province and therefore, the importance of this assessment with regards to safety.Scattered seismic anomalies are observed within the Cenozoic sedimentary succession covering the rift basins of the Melville Bay region. These features, potentially representing the presence of free gas or gas-rich fluids, vary in nature from isolated anomalies, fault flags, stacked fluid flow features and canyons; all of which pose a significant drilling risk and were actively avoided during site selection. In areas above the Melville Bay Ridge &#8211; a feature that dominates the structure of this area &#8211; free gas is also observed trapped beneath extensive gas hydrate deposits, identified via a spectacularly imaged bottom simulating reflector marking the base of the gas hydrate stability zone. The location of the hydrate deposits, and the free gas beneath, are likely controlled by a complicated migration history, due to large scale rift-related faulting and migration along sandy aquifer horizons. In other areas, gas is interpreted to have reached the shallow subsurface due to secondary leakage from a deeper gas reservoir on the ridge crest.It is clear that hydrocarbon related hazards within this area are varied and abundant, making it a more challenging location to select sites for an IODP drilling campaign. However, due to the extensive coverage and high resolution (up to 11 m vertical resolution (45 Hz at 2.0 km/s velocity) of the 3D seismic data available, as well as the use of recently acquired ultra-high resolution site survey lines, these features can be accurately imaged and confidently mapped. This allowed for the development of a detailed understanding of the character and distribution of fluids within the shallow subsurface, and the use of this knowledge to select site localities that maximise the potential for drilling to be completed safely and successfully if proposal 909 were to be executed.

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Spatiotemporal variability of the gas transfer coefficient (KCO2) in boreal streams: Implications for large scale estimates of CO2evasion

Global Biogeochemical Cycles ◽

10.1029/2010gb003975 ◽

2011 ◽

Vol 25 (3) ◽

pp. n/a-n/a ◽

Cited By ~ 88

Author(s):

Marcus B. Wallin ◽

Mats G. Öquist ◽

Ishi Buffam ◽

Michael F. Billett ◽

Jakob Nisell ◽

...

Keyword(s):

Transfer Coefficient ◽

Large Scale ◽

Spatiotemporal Variability ◽

Gas Transfer ◽

Boreal Streams ◽

Gas Transfer Coefficient

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Beyond halo mass: quenching galaxy mass assembly at the edge of filaments

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3981 ◽

2020 ◽

Author(s):

Hyunmi Song ◽

Clotilde Laigle ◽

Ho Seong Hwang ◽

Julien Devriendt ◽

Yohan Dubois ◽

...

Keyword(s):

Large Scale ◽

Mass Effect ◽

Gas Transfer ◽

Scale Analysis ◽

Quenching Mechanism ◽

Multi Scale ◽

Close Proximity ◽

Mass Assembly ◽

Multi Scale Analysis ◽

Negligible Influence

Abstract We examine how the mass assembly of central galaxies depends on their location in the cosmic web. The Horizon-AGN simulation is analysed at z ∼ 2 using the DisPerSE code to extract multi-scale cosmic filaments. We find that the dependency of galaxy properties on large-scale environment is mostly inherited from the (large-scale) environmental dependency of their host halo mass. When adopting a residual analysis that removes the host halo mass effect, we detect a direct and non-negligible influence of cosmic filaments. Proximity to filaments enhances the build-up of stellar mass, a result in agreement with previous studies. However, our multi-scale analysis also reveals that, at the edge of filaments, star formation is suppressed. In addition, we find clues for compaction of the stellar distribution at close proximity to filaments. We suggest that gas transfer from the outside to the inside of the haloes (where galaxies reside) becomes less efficient closer to filaments, due to high angular momentum supply at the vorticity-rich edge of filaments. This quenching mechanism may partly explain the larger fraction of passive galaxies in filaments, as inferred from observations at lower redshifts.

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Measuring air–sea gas-exchange velocities in a large-scale annular wind–wave tank

Ocean Science ◽

10.5194/os-11-121-2015 ◽

2015 ◽

Vol 11 (1) ◽

pp. 121-138 ◽

Cited By ~ 9

Author(s):

E. Mesarchaki ◽

C. Kräuter ◽

K. E. Krall ◽

M. Bopp ◽

F. Helleis ◽

...

Keyword(s):

Gas Exchange ◽

Large Scale ◽

Wind Wave ◽

Chemical Species ◽

Surface States ◽

Gas Transfer ◽

Transfer Velocity ◽

Wave Tank ◽

Wide Range ◽

Triton X

Abstract. In this study we present gas-exchange measurements conducted in a large-scale wind–wave tank. Fourteen chemical species spanning a wide range of solubility (dimensionless solubility, α = 0.4 to 5470) and diffusivity (Schmidt number in water, Scw = 594 to 1194) were examined under various turbulent (u10 = 0.73 to 13.2 m s−1) conditions. Additional experiments were performed under different surfactant modulated (two different concentration levels of Triton X-100) surface states. This paper details the complete methodology, experimental procedure and instrumentation used to derive the total transfer velocity for all examined tracers. The results presented here demonstrate the efficacy of the proposed method, and the derived gas-exchange velocities are shown to be comparable to previous investigations. The gas transfer behaviour is exemplified by contrasting two species at the two solubility extremes, namely nitrous oxide (N2O) and methanol (CH3OH). Interestingly, a strong transfer velocity reduction (up to a factor of 3) was observed for the relatively insoluble N2O under a surfactant covered water surface. In contrast, the surfactant effect for CH3OH, the high solubility tracer, was significantly weaker.

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Global ocean carbon uptake: magnitude, variability and trends

Biogeosciences Discussions ◽

10.5194/bgd-9-10961-2012 ◽

2012 ◽

Vol 9 (8) ◽

pp. 10961-11012 ◽

Cited By ~ 14

Author(s):

R. Wanninkhof ◽

G.-H. Park ◽

T. Takahashi ◽

C. Sweeney ◽

R. Feely ◽

...

Keyword(s):

Interannual Variability ◽

General Circulation ◽

Large Scale ◽

Methodological Issue ◽

Co2 Flux ◽

Global Ocean ◽

Gas Transfer ◽

Co2 Uptake ◽

Anthropogenic Co2 ◽

Inverse Models

Abstract. Estimates of the anthropogenic global-integrated sea-air carbon dioxide (CO2) flux from 1990 to 2009, based on different models and measurements, range from –1.4 to –2.6 Pg C yr–1. The median values of anthropogenic CO2 for each method show better agreement and are: −1.9 for Pg C yr−1 for numerical ocean general circulation hind cast models (OGCMs) with parameterized biogeochemistry; –2.1 Pg C yr–1 for atmospheric inverse models; –1.9 Pg C yr–1 for global atmospheric constraints based on O2 / N2 ratios for 1990–2000; and –2.4 Pg C yr–1 for oceanic inverse models. An updated estimate of this anthropogenic CO2 flux based on a climatology of sea-air partial pressure of CO2 differences (ΔpCO2) (Takahashi et al., 2009) and a bulk formulation of gas transfer with wind speed for year 2000 is –2.0 Pg C yr–1. Using this ΔpCO2 climatology and empirical relationships of pCO2 with sea-surface temperature (SST) anomalies (Park et al., 2010a), the interannual variability of the contemporary CO2 flux is estimated to be 0.20 Pg C yr–1 (1σ) from 1990 through 2009. This is similar to the variability estimated by the OGCMs of 0.16 Pg C yr–1 but smaller than the interannual variability from atmospheric inverse estimates of 0.40 Pg C yr–1. The variability is largely driven by large-scale climate re-organizations. The decadal trends for different methods range from –0.13 (Pg C yr–1) decade–1 to –0.50 (Pg C yr−1) decade−1. The OGCMs and the data based sea-air CO2 flux estimates show smaller uptakes and appreciably smaller decadal trends than estimates based on changes in carbon inventory suggesting that methods capable of resolving shorter timescales are showing a slowing of the rate of ocean CO2 uptake. It is not clear if this large difference in trend is a methodological issue or a real natural feedback.

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Experimental Observations of Turbulent Events in the Surfzone

Journal of Marine Science and Engineering ◽

10.3390/jmse7100332 ◽

2019 ◽

Vol 7 (10) ◽

pp. 332 ◽

Cited By ~ 3

Author(s):

De Serio ◽

Mossa

Keyword(s):

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Large Scale ◽

Surf Zone ◽

Breaking Waves ◽

Gas Transfer ◽

Principal Characteristics ◽

Sea Bottom ◽

Elevation Data ◽

Water Gas

In coastal dynamics, large-scale eddies transport and spread smaller turbulent vortices both towards the sea surface, thus contributing to the processes of air-water gas transfer, and towards the sea bottom, inducing sediment pick-up and resuspension. The mechanical role of the breaking-induced vortices to the redistribution of turbulence and turbulent kinetic energy is still unclear and needs a more thorough study, possibly supported by more measurements in this field. Based on this, the present paper aims to investigate the effects of experimental breaking waves in the surf zone. Two regular breaking waves, a spiller and a plunger, which propagate on a fixed slope, were generated in a laboratory channel and were examined shoreward to the breaker line. The measurements of their velocities in the cross-shore plane were assessed by means of a 2D Laser Doppler Anemometer. At the same time and location, elevation data were also acquired using a resistive wave gauge. Here, the principal characteristics are addressed in terms of turbulent intensities, turbulent kinetic energy, length scales and coherent motions. Our results could thus contribute to better define conceptual models used in typical engineering applications in coastal areas.

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Measuring air–sea gas exchange velocities in a large scale annular wind-wave tank

Ocean Science Discussions ◽

10.5194/osd-11-1643-2014 ◽

2014 ◽

Vol 11 (3) ◽

pp. 1643-1689 ◽

Cited By ~ 3

Author(s):

E. Mesarchaki ◽

C. Kräuter ◽

K. E. Krall ◽

M. Bopp ◽

F. Helleis ◽

...

Keyword(s):

Gas Exchange ◽

Large Scale ◽

Wind Wave ◽

Chemical Species ◽

Surface States ◽

Gas Transfer ◽

Transfer Velocity ◽

Wave Tank ◽

Wide Range ◽

Triton X

Abstract. In this study we present gas exchange measurements conducted in a large scale wind-wave tank. Fourteen chemical species spanning a wide range of solubility (dimensionless solubility, α = 0.4 to 5470) and diffusivity (Schmidt number in water, Scw = 594 to 1194) were examined under various turbulent (u10 = 0.8 to 15 m s−1 conditions. Additional experiments were performed under different surfactant modulated (two different concentration levels of Triton X-100) surface states. This paper details the complete methodology, experimental procedure and instrumentation used to derive the total transfer velocity for all examined tracers. The results presented here demonstrate the efficacy of the proposed method, and the derived gas exchange velocities are shown to be comparable to previous investigations. The gas transfer behaviour is exemplified by contrasting two species at the two solubility extremes, namely nitrous oxide (N2O) and methanol (CH3OH). Interestingly, a strong transfer velocity reduction (up to a factor of three) was observed for N2O under a surfactant covered water surface. In contrast, the surfactant affected CH3OH, the high solubility tracer only weakly.

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