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Turbulent ‘stopping plumes’ and plume pinch-off in uniform surroundings

Kattimeri, Athina; Scase, Matthew M.

Authors

Athina Kattimeri akattimeri@yahoo.co.uk



Abstract

Observations of turbulent convection in the environment are of variously sus- tained plume-like flows or intermittent thermal-like flows. At different times of the day the prevailing conditions may change and consequently the observed flow regimes may change. Understanding the link between these flows is of practical importance meteorologically, and here we focus our interest upon plume-like regimes that break up to form thermal-like regimes. It has been shown that when a plume rises from a boundary with low conductivity, such as arable land, the inability to maintain a rapid enough supply of buoyancy to the plume source can result in the turbulent base of the plume separating and rising away from the source. This plume ‘pinch-off’ marks the onset of the intermittent thermal-like behavior. The dynamics of turbulent plumes in a uniform environment are explored in order to investigate the phenomenon of plume pinch-off. The special case of a turbulent plume having its source completely removed, a ‘stopping plume’, is considered in particular. The effects of forcing a plume to pinch-off, by rapidly reducing the source buoyancy flux to zero, are shown experi- mentally. We release saline solution into a tank filled with fresh water generating downward propagating steady turbulent plumes. By rapidly closing the plume nozzle, the plumes are forced to pinch-off. The plumes are then observed to detach from the source and descend into the ambient. The unsteady buoyant region produced after pinch-off, cannot be described by the power-law behavior of either classical plumes or thermals, and so the terminology ‘stopping plume’ (analogous to a ‘starting plume’) is adopted for this type of flow. The propagation of the stopping plume is shown to be approximately linearly dependent on time, and we speculate therefore that the closure of the nozzle introduces some vorticity into the ambient, that may roll up to form a vortex ring dominating the dynamics of the base of a stopping plume.

Citation

Kattimeri, A., & Scase, M. M. (2014). Turbulent ‘stopping plumes’ and plume pinch-off in uniform surroundings. Environmental Fluid Mechanics, 15(5), doi:10.1007/s10652-014-9387-7

Journal Article Type Article
Publication Date Sep 27, 2014
Deposit Date Sep 18, 2015
Publicly Available Date Sep 18, 2015
Journal Environmental Fluid Mechanics
Print ISSN 1567-7419
Electronic ISSN 1567-7419
Publisher Humana Press
Peer Reviewed Peer Reviewed
Volume 15
Issue 5
DOI https://doi.org/10.1007/s10652-014-9387-7
Public URL http://eprints.nottingham.ac.uk/id/eprint/30169
Publisher URL http://link.springer.com/article/10.1007%2Fs10652-014-9387-7
Copyright Statement Copyright information regarding this work can be found at the following address: http://eprints.nottingh.../end_user_agreement.pdf
Additional Information The final publication is available at Springer via http://dx.doi.org/10.1007/s10652-014-9387-7

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://eprints.nottingham.ac.uk/end_user_agreement.pdf





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