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  • 1
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    Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank (2015)
    Copernicus
    Details
    Publication Date: 2015-01-26
    Description: A comparative study of simultaneous heat and gas exchange measurements was performed in the large annular Heidelberg Air–Sea Interaction Facility, the Aeolotron, under homogeneous water surface conditions. The use of two gas tracers, N2O and C2HF5, resulted not only in gas transfer velocities, but also in the measurement of the Schmidt number exponent n with a precision of ±0.025. The original controlled flux, or active thermographic, technique proposed by Jähne et al. (1989) was applied by heating a large patch at the water surface to measure heat transfer velocities. Heating a large patch, the active thermography technique is laterally homogeneous, and problems of lateral transport effects are avoided. Using the measured Schmidt number exponents, the ratio of the scaled heat transfer velocities to the measured gas transfer velocities is 1.046 ± 0.040, a good agreement within the limits of experimental uncertainties. This indicates the possibility to scale heat transfer velocities measured by active thermography to gas transfer velocities, provided that the Schmidt number exponent is known and that the heated patch is large enough to reach the thermal equilibrium.
    Print ISSN: 1812-0784
    Electronic ISSN: 1812-0792
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 2
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    Measuring air–sea gas-exchange velocities in a large-scale annular wind–wave tank (2015)
    Copernicus
    Details
    Publication Date: 2015-01-28
    Description: 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.
    Print ISSN: 1812-0784
    Electronic ISSN: 1812-0792
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 3
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    First laboratory study of air–sea gas exchange at hurricane wind speeds (2014)
    Copernicus
    Details
    Publication Date: 2014-04-23
    Description: In a pilot study conducted in October and November 2011, air–sea gas transfer velocities of the two sparingly soluble trace gases hexafluorobenzene and 1,4-difluorobenzene were measured in the unique high-speed wind-wave tank at Kyoto University, Japan. This air–sea interaction facility is capable of producing hurricane strength wind speeds of up to u10 =67 m s−1. This constitutes the first lab study of gas transfer at such high wind speeds. The measured transfer velocities k600 spanned two orders of magnitude, lying between 11 cm h−1 and 1180 cm h−1 with the latter being the highest ever measured wind-induced gas transfer velocity. The measured gas transfer velocities are in agreement with the only available data set at hurricane wind speeds (McNeil and D'Asaro, 2007). The disproportionately large increase of the transfer velocities found at highest wind speeds indicates a new regime of air–sea gas transfer, which is characterized by strong wave breaking, enhanced turbulence and bubble cloud entrainment.
    Print ISSN: 1812-0784
    Electronic ISSN: 1812-0792
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 4
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    Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank (2014)
    Copernicus
    Details
    Publication Date: 2014-06-25
    Description: A comparative study of simultaneous heat and gas exchange measurements was performed in the large annular Heidelberg Air–Sea Interaction Facility, the Aeolotron, under homogeneous water surface conditions. The use of two gas tracers, N2O and C2HF5, resulted not only in gas transfer velocities, but also in the measurement of the Schmidt number exponent n with a precision of ± 0.025. The original controlled flux or active thermographic technique proposed by Jähne et al. (1989) was applied by heating a large patch at the water surface to measure heat transfer velocities. Heating a large patch, the active thermography technique is laterally homogeneous and problems of lateral transport effects are avoided. Using the measured Schmidt number exponents, the ratio of the scaled heat transfer velocities to the measured gas transfer velocities is 1.046 ± 0.040, a good agreement within the limits of experimental uncertainties. This indicates the possibility to scale heat transfer velocities measured by active thermography to gas transfer velocities, provided the Schmidt number exponent is known and that the heated patch is large enough to reach the thermal equilibrium.
    Print ISSN: 1812-0806
    Electronic ISSN: 1812-0822
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 5
    facet.materialart.
    Unknown
    Measuring air–sea gas exchange velocities in a large scale annular wind-wave tank (2014)
    Copernicus
    Details
    Publication Date: 2014-06-23
    Description: 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.
    Print ISSN: 1812-0806
    Electronic ISSN: 1812-0822
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
    facet.materialart.
    Unknown
    First air–sea gas exchange laboratory study at hurricane wind speeds (2013)
    Copernicus
    Details
    Publication Date: 2013-11-05
    Description: In a pilot study conducted in October and November 2011, air–sea gas transfer velocities of the two sparingly soluble trace gases hexafluorobenzene and 1,4-difluorobenzene were measured in the unique High-Speed Wind-Wave Tank at Kyoto University, Japan. This air–sea interaction facility is capable of producing hurricane strength wind speeds of up to u10=67 m s−1. This constitutes the first lab study of gas transfer at such high wind speeds. The measured transfer velocities k600 spanned two orders of magnitude, lying between 11 cm h−1 and 1180 cm h−1 with the latter being the highest ever measured wind induced gas transfer velocity. The measured gas transfer velocities are in agreement with the only available dataset at hurricane wind speeds (McNeil and D'Asaro, 2007). The disproportionately large increase of the transfer velocities found at highest wind speeds indicates a new regime of air–sea gas transfer, which is characterized by strong wave breaking, enhanced turbulence and bubble cloud entrainment. It was found that tracers spanning a wide range of solubilities and diffusivities are needed to separate the effects of enhanced surface area and turbulence due to breaking waves from the effects of bubble and spray mediated gas transfer.
    Print ISSN: 1812-0806
    Electronic ISSN: 1812-0822
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
    facet.materialart.
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    Measuring air–sea gas exchange velocities in a large scale annular wind-wave tank (2015)
    Copernicus Publications (EGU)
    In:  Ocean Science, 11 . pp. 121-138.
    Details
    Publication Date: 2015-05-28
    Description: 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
    Type: Article , PeerReviewed
    Format: text
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    PAPER (OCEANREP)
  • 8
    facet.materialart.
    Unknown
    Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank (2015)
    Copernicus Publications (EGU)
    In:  Ocean Science, 11 . pp. 111-120.
    Details
    Publication Date: 2015-05-28
    Description: A comparative study of simultaneous heat and gas exchange measurements was performed in the large annular Heidelberg Air–Sea Interaction Facility, the Aeolotron, under homogeneous water surface conditions. The use of two gas tracers, N2O and C2HF5, resulted not only in gas transfer velocities, but also in the measurement of the Schmidt number exponent n with a precision of ± 0.025. The original controlled flux or active thermographic technique proposed by Jähne et al. (1989) was applied by heating a large patch at the water surface to measure heat transfer velocities. Heating a large patch, the active thermography technique is laterally homogeneous and problems of lateral transport effects are avoided. Using the measured Schmidt number exponents, the ratio of the scaled heat transfer velocities to the measured gas transfer velocities is 1.046 ± 0.040, a good agreement within the limits of experimental uncertainties. This indicates the possibility to scale heat transfer velocities measured by active thermography to gas transfer velocities, provided the Schmidt number exponent is known and that the heated patch is large enough to reach the thermal equilibrium.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
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    PAPER (OCEANREP)
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