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| Titel |
Structure of Small-Scale Turbulences at the Free Air-Water Interface |
| VerfasserIn |
C. Garbe, J. Schnieders |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065649
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| Zusammenfassung |
| In this contribution we will present a new approach for analyzing interfacial shear induced
turbulence at the free air-water interface. We use an infrared imager sensitive in
the spectral range form 3-5 μm for visualizing the water sided turbulence from
passive thermography. Due to a heat flux present at the interface, a temperature
difference exists between the skin layer and the water bulk below the diffusive
sub-layer. Turbulence disrupts the boundary layer, the temperature footprint of which
can be seen in the images. Due to the shear at the interface, turbulences are not
isotropic but exhibit elongated streaks in wind direction. We will present a novel image
processing based approach for classifying and segmenting the streaks. From these
segmentation, statistical distributions of streak spacings can be analyzed. As expected, a
trend towards smaller streak spacings with increasing friction velocity is evident.
Surprisingly, above a certain threshold friction velocity, streak spacings appear
to remain constant. Besides small-scale structures, we also examine larger scale
coherent structures, which can be associated with Langmuir circulations. We relate our
findings to the Langmuir number for a first indication of the production processes of
these structures. Results from laboratory and field measurements will be presented. |
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