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| Titel |
Comparison of velocity and temperature time series data analysis in experiments on the thermally driven rotating annulus |
| VerfasserIn |
Thomas von Larcher, Uwe Harlander, Kiril Alexandrov, Yongtai Wang |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042462
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| Zusammenfassung |
| The model of the differentially heated, rotating cylindrical gap filled with a fluid is since more
than four decades extensively used for laboratory experiments of baroclinic wave
interactions, and a number of data acquisition techniques are applied e.g. to unhide regular
waves of different zonal wave number, to better understand the transition to the
quasi-chaotic regime, and to reveal the underlying dynamical processes of complex wave
flows.
In our experiments presented here, we make use of non-intrusive measurement techniques
of a quite different nature. While the high accurate Laser-Doppler-Velocimetry (LDV ) is
used for measurements of the radial velocity component at equidistant azimuthal positions, a
high sensitive thermographic camera, which resolution allows for resolving fine scale
structures, measures the surface temperature field.
Both sets of time series data are analyzed by using multivariate statistical techniques.
While the LDV data sets are studied by applying the Multi-Channel Singular Spectrum
Analysis (M - SSA), the temperature data sets are analyzed by applying the Empirical
Orthogonal Functions (EOF ).
In addition, the temperature data are processed in a way to become comparable to the
LDV data, i.e. reducing the size of the data set in such a manner that the temperature
measurements would imaginary be performed at equidistant azimuthal positions
only. This approach initially results in a great loss of information. But applying the
M - SSA to the reduced temperature data sets enable us not only to compare the
data analysis methods but also to reclassify the results yielded with the LDV data
analysis.
The measurements are performed at particular parameter points, where our former studies
show that kinds of complex wave patterns occur [1, 2]. For example, we found a dominant
and a weak mode in the 3-4 wave transition region. This finding confirms earlier ideas on
wave dispersion in transition regions between regular waves. Increasing the annulus’
rotation leads to a growth of the weak mode until this mode becomes the dominant
one.
[1] Th. von Larcher and C. Egbers, Experiments on transitions of baroclinic waves in a
differentially heated rotating annulus, Nonlinear Processes in Geophysics, 2005, 12,
1033-1041, NPG Print: ISSN 1023-5809, NPG Online: ISSN 1607-7946
[2] U. Harlander, Th. von Larcher, Y. Wang and C. Egbers, PIV- and LDV-measurements of
baroclinic wave interactions in a thermally driven rotating annulus, Experiments in Fluids,
2009, DOI: 10.1007/s00348-009-0792-5 |
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