Mechanism of drag coefficient saturation at strong wind speeds

Previous studies have demonstrated the saturation of drag coefficients at strong wind speeds. But the mechanism behind this saturation has not yet been fully clarified. In this study, at normal and strong wind speeds, we use a wind‐wave tank for investigating the peak enhancement factor of the wind‐...

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Bibliographic Details
Published in:Geophysical research letters 2016-09, Vol.43 (18), p.9829-9835
Main Authors: Takagaki, Naohisa, Komori, Satoru, Suzuki, Naoya, Iwano, Koji, Kurose, Ryoichi
Format: Article
Language:English
Subjects:
Age
air‐sea interaction
Breaking
Coefficients
Drag
Drag coefficient
Drag coefficients
Flatness
Fluctuation
Gauges
Geophysics
Inverse
Measuring instruments
Saturation
Tanks
Tornadoes
tropical cyclone
Water level fluctuations
Wave breaking
Wave measuring equipment
Wave tanks
Wind speed
Wind waves
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Summary:Previous studies have demonstrated the saturation of drag coefficients at strong wind speeds. But the mechanism behind this saturation has not yet been fully clarified. In this study, at normal and strong wind speeds, we use a wind‐wave tank for investigating the peak enhancement factor of the wind‐sea spectrum, which is an appropriate wave parameter for representing interfacial flatness. We measured the water‐level fluctuation using wave gauges. At strong wind speeds, the result shows that the peak enhancement factor of the wind‐sea spectrum decreases with decreasing inverse wave age and with increasing wind speed. This suggests that the distinctive wind‐wave breaking occurs at strong wind speeds. It also suggests that this distinctive breaking of wind waves causes the saturation of drag coefficients at strong wind speeds. Key Points The peak enhancement factor in a wind‐wave tank is measured New correlations about the peak enhancement factor of the wind‐sea spectrum are proposed Drag saturation at extremely high wind speeds is determined to be caused by distinctive wave breaking
ISSN:0094-8276
1944-8007
DOI:10.1002/2016GL070666