CUED Publications database

The evolution of a stratified turbulent cloud

Maffioli, A and Davidson, PA and Dalziel, SB and Swaminathan, N (2014) The evolution of a stratified turbulent cloud. Journal of Fluid Mechanics, 739. pp. 229-253. ISSN 0022-1120

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Abstract

Localized regions of turbulence, or turbulent clouds, in a stratified fluid are the subject of this study, which focuses on the edge dynamics occurring between the turbulence and the surrounding quiescent region. Through laboratory experiments and numerical simulations of stratified turbulent clouds, we confirm that the edge dynamics can be subdivided into materially driven intrusions and horizontally travelling internal wave-packets. Three-dimensional visualizations show that the internal gravity wave-packets are in fact large-scale pancake structures that grow out of the turbulent cloud into the adjacent quiescent region. The wave-packets were tracked in time, and it is found that their speed obeys the group speed relation for linear internal gravity waves. The energetics of the propagating waves, which include waveforms that are inclined with respect to the horizontal, are also considered and it is found that, after a period of two eddy turnover times, the internal gravity waves carry up to 16 % of the cloud kinetic energy into the initially quiescent region. Turbulent events in nature are often in the form of decaying turbulent clouds, and it is therefore suggested that internal gravity waves radiated from an initial cloud could play a significant role in the reorganization of energy and momentum in the atmosphere and oceans.©2013 Cambridge University Press.

Item Type: Article
Uncontrolled Keywords: Geophysical and geological flows Internal waves Stratified turbulence
Subjects: UNSPECIFIED
Divisions: Div A > Energy
Div A > Fluid Mechanics
Div A > Turbomachinery
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 12:03
Last Modified: 08 Dec 2014 02:16
DOI: 10.1017/jfm.2013.612