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| Titel |
Dynamics of turbulence under the effect of stratification and internal waves |
| VerfasserIn |
O. A. Druzhinin, L. A. Ostrovsky |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2198-5634
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics Discussions ; 2, no. 1 ; Nr. 2, no. 1 (2015-02-19), S.329-359 |
| Datensatznummer |
250115150
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| Publikation (Nr.) |
 copernicus.org/npgd-2-329-2015.pdf |
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| Zusammenfassung |
| The objective of this paper is to study the dynamics of small-scale turbulence near a pycnocline, both in the free regime and
under the action of an internal gravity wave (IW) propagating along a pycnocline, using direct numerical simulation
(DNS). Turbulence is initially induced in a horizontal layer at some distance above the pycnocline. The velocity and density
fields of IW propagating in the pycnocline are also prescribed as initial condition. The IW wavelength is considered to be by the
order of magnitude larger as compared to the initial turbulence integral length scale. Stratification in the pycnocline is
considered to be sufficiently strong so that the effects of turbulent mixing remain negligible. The dynamics of turbulence is
studied both with and without initially induced internal wave. The DNS results show that in the absence of IW turbulence decays,
but its decay rate is reduced in the vicinity of the pycnocline where stratification effects are significant. In this case, at
sufficiently late times most of turbulent energy is located in a layer close to the pycnocline center. Here turbulent eddies are
collapsed in the vertical direction and acquire the "pancake" shape. IW modifies turbulence dynamics, in that the turbulence
kinetic energy (TKE) is significantly enhanced as compared to the TKE in the absence of IW. As in the case without IW, most of
turbulent energy is localized in the vicinity of the pycnocline center. Here the TKE spectrum is considerably enhanced in the
entire wavenumber range as compared to the TKE spectrum in the absence of IW. |
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