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| Titel |
On the entrainment coefficient in a forced plume: quantitative effects of source parameters |
| VerfasserIn |
A. Matulka, P. Lopez, J. M. Redondo, A. Tarquis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 21, no. 1 ; Nr. 21, no. 1 (2014-02-24), S.269-278 |
| Datensatznummer |
250120890
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| Publikation (Nr.) |
 copernicus.org/npg-21-269-2014.pdf |
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| Zusammenfassung |
| The behavior of a forced plume is mainly controlled by the source buoyancy
and momentum fluxes and the efficiency of turbulent mixing between the plume
and the ambient fluid (stratified or not). The interaction between the plume
and the ambient fluid controls the plume dynamics and is usually represented
by the entrainment coefficient αE. Commonly used
one-dimensional models incorporating a constant entrainment coefficient are
fundamental and very useful for predictions in geophysical flows and
industrial situations. Nevertheless, if the basic geometry of the flow
changes, or the type of source or the environmental fluid conditions (e.g.,
level of turbulence, shear, ambient stratification, presence of internal
waves), new models allowing for variable entrainment are necessary. The
presented paper is an experimental study based on a set of turbulent plume
experiments in a calm unstratified ambient fluid under different source
conditions (represented by different buoyancy and momentum fluxes). The main
result is that the entrainment coefficient is not a constant and clearly
varies in time within the same plume independently of the buoyancy and the
source position. This paper also analyzes the influence of the source
conditions on the mentioned time evolution. The measured entrainment
coefficient αE has considerable variability. It ranges
between 0.26 and 0.9 for variable Atwood number experiments and between 0.16
and 0.55 for variable source position experiments. As is observed, values are
greater than the traditional standard value of Morton et al. (1956) for
plumes and jets, which is about 0.13. |
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