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    Wind Stress Measurements from the Open Ocean Corrected for Airflow Distortion by the Ship

    Source: Journal of Physical Oceanography:;1998:;Volume( 028 ):;issue: 007::page 1511
    Author:
    Yelland, M. J.
    ,
    Moat, B. I.
    ,
    Taylor, P. K.
    ,
    Pascal, R. W.
    ,
    Hutchings, J.
    ,
    Cornell, V. C.
    DOI: 10.1175/1520-0485(1998)028<1511:WSMFTO>2.0.CO;2
    Publisher: American Meteorological Society
    Abstract: A large dataset of wind stress estimates, covering a wide range of wind speed and stability conditions, was obtained during three cruises of the RRS Discovery in the Southern Ocean. These data were used by Yelland and Taylor to determine the relationship between 10-m height, neutral stability values for the drag coefficient, and the wind speed, and to devise a new formulation for the nondimensional dissipation function under diabatic conditions. These results have been reevaluated allowing for the airflow distortion caused by the ship. The acceleration and vertical displacement of the flow have been modeled in three dimensions using computational fluid dynamics (CFD). The CFD modeling was tested, first by comparison with wind tunnel measurements on models of two Canadian research ships and second, by analysis of data from four anemometers on the foremast of the RRS Charles Darwin. Originally, the four anemometers gave drag coefficient values that differed by up to 20% from one to another and were all unexpectedly high. The CFD results showed that the airflow had been decelerated by 4%?14% and displaced vertically by about 1 m. These effects caused the original drag coefficient results to be overestimated by up to 60%. After correcting for flow distortion effects, the results from the different anemometers became consistent, which gave confidence in the quantitative CFD-derived corrections. The CFD modeling showed that the anemometer position on the RRS Discovery was much less affected by airflow distortion. For a given wind speed the CFD corrections reduced the drag coefficient by about 6%. The resulting mean drag coefficient to wind speed relationship confirmed that suggested by Smith from a more limited set of open ocean data. The effects of flow distortion are sensitive to changes in the relative wind direction. It is shown that much of the scatter in drag coefficient estimates may be due to variations in airflow distortion rather than to the effect of changing sea states. The Discovery wind stress data is examined for evidence of a sea-state dependence: none is found. It is concluded that a wave-age-dependent wind stress formulation is not applicable to open ocean conditions.
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      Wind Stress Measurements from the Open Ocean Corrected for Airflow Distortion by the Ship

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    http://yetl.yabesh.ir/yetl1/handle/yetl/4166072
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    contributor authorYelland, M. J.
    contributor authorMoat, B. I.
    contributor authorTaylor, P. K.
    contributor authorPascal, R. W.
    contributor authorHutchings, J.
    contributor authorCornell, V. C.
    date accessioned2017-06-09T14:53:06Z
    date available2017-06-09T14:53:06Z
    date copyright1998/07/01
    date issued1998
    identifier issn0022-3670
    identifier otherams-28904.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4166072
    description abstractA large dataset of wind stress estimates, covering a wide range of wind speed and stability conditions, was obtained during three cruises of the RRS Discovery in the Southern Ocean. These data were used by Yelland and Taylor to determine the relationship between 10-m height, neutral stability values for the drag coefficient, and the wind speed, and to devise a new formulation for the nondimensional dissipation function under diabatic conditions. These results have been reevaluated allowing for the airflow distortion caused by the ship. The acceleration and vertical displacement of the flow have been modeled in three dimensions using computational fluid dynamics (CFD). The CFD modeling was tested, first by comparison with wind tunnel measurements on models of two Canadian research ships and second, by analysis of data from four anemometers on the foremast of the RRS Charles Darwin. Originally, the four anemometers gave drag coefficient values that differed by up to 20% from one to another and were all unexpectedly high. The CFD results showed that the airflow had been decelerated by 4%?14% and displaced vertically by about 1 m. These effects caused the original drag coefficient results to be overestimated by up to 60%. After correcting for flow distortion effects, the results from the different anemometers became consistent, which gave confidence in the quantitative CFD-derived corrections. The CFD modeling showed that the anemometer position on the RRS Discovery was much less affected by airflow distortion. For a given wind speed the CFD corrections reduced the drag coefficient by about 6%. The resulting mean drag coefficient to wind speed relationship confirmed that suggested by Smith from a more limited set of open ocean data. The effects of flow distortion are sensitive to changes in the relative wind direction. It is shown that much of the scatter in drag coefficient estimates may be due to variations in airflow distortion rather than to the effect of changing sea states. The Discovery wind stress data is examined for evidence of a sea-state dependence: none is found. It is concluded that a wave-age-dependent wind stress formulation is not applicable to open ocean conditions.
    publisherAmerican Meteorological Society
    titleWind Stress Measurements from the Open Ocean Corrected for Airflow Distortion by the Ship
    typeJournal Paper
    journal volume28
    journal issue7
    journal titleJournal of Physical Oceanography
    identifier doi10.1175/1520-0485(1998)028<1511:WSMFTO>2.0.CO;2
    journal fristpage1511
    journal lastpage1526
    treeJournal of Physical Oceanography:;1998:;Volume( 028 ):;issue: 007
    contenttypeFulltext
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