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  Vertical drafts and mixing in stratified turbulence: Sharp transition with Froude number

Feraco, F., Marino, R., Pumir, A., Primavera, L., Mininni, P. D., Pouquet, A., et al. (2018). Vertical drafts and mixing in stratified turbulence: Sharp transition with Froude number. EPL-Europhysics Letters, 123(4): 44002. doi:10.1209/0295-5075/123/44002.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0002-47AF-A Version Permalink: http://hdl.handle.net/21.11116/0000-0003-ADC7-A
Genre: Journal Article

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Feraco, F., Author
Marino, R., Author
Pumir, Alain1, Author              
Primavera, L., Author
Mininni, P. D., Author
Pouquet, A., Author
Rosenberg, D., Author
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1Laboratory for Fluid Dynamics, Pattern Formation and Biocomplexity, Max Planck Institute for Dynamics and Self-Organization, Max Planck Society, ou_2063287              

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 Abstract: We investigate the large-scale intermittency of vertical velocity and temperature, and the mixing properties of stably stratified turbulent flows using both Lagrangian and Eulerian fields from direct numerical simulations of the Boussinesq equations with periodic boundary conditions, in a parameter space relevant for the atmosphere and the oceans. Over a range of F'roude numbers of geophysical interest (approximate to 0.05-0.3) we observe very large fluctuations of the vertical components of the velocity and the potential temperature, localized in space and time, with a sharp transition leading to non-Gaussian wings of the probability distribution functions. This behavior is captured by a simple model representing the competition between gravity waves on a fast time scale and nonlinear steepening on a slower time scale. The existence of a resonant regime characterized by enhanced large-scale intermittency, as understood within the framework of the proposed model, is then linked to the emergence of structures in the velocity and potential temperature fields, localized overturning and mixing. Finally, in the same regime we observe a linear scaling of the mixing efficiency with the Froude number and an increase of its value of roughly one order of magnitude.

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Language(s): eng - English
 Dates: 2018-09-182018-08
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: Peer
 Identifiers: DOI: 10.1209/0295-5075/123/44002
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Title: EPL-Europhysics Letters
Source Genre: Journal
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Pages: 7 Volume / Issue: 123 (4) Sequence Number: 44002 Start / End Page: - Identifier: -