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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 |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 22, no. 3 ; Nr. 22, no. 3 (2015-06-04), S.337-348 |
| Datensatznummer |
250120984
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| Publikation (Nr.) |
 copernicus.org/npg-22-337-2015.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 IWs propagating in the pycnocline are also prescribed as an initial
condition. The IW wavelength is considered to be larger by the order of
magnitude 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 an initially induced IW. The DNS
results show that, in the absence of an 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
the 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 the turbulent
energy is localized in the vicinity of the pycnocline center. Here, the TKE
spectrum is considerably enhanced in the entire wave-number range as compared
to the TKE spectrum in the absence of IW. |
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