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Stability transitions and turbulence in horizontal convection

Gayen, Bishakhdatta; Griffiths, Ross; Hughes, Graham

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Recent results have shown that convection forced by a temperature gradient along one horizontal boundary of a rectangular domain at a large Rayleigh number can be turbulent in parts of the flow field. However, the conditions for onset of turbulence, the dependence of flow and heat transport on Rayleigh number, and the roles of large and small scales in the flow, have not been established. We use three-dimensional direct numerical simulation (DNS) and large-eddy simulation (LES) over a wide...[Show more]

dc.contributor.authorGayen, Bishakhdatta
dc.contributor.authorGriffiths, Ross
dc.contributor.authorHughes, Graham
dc.date.accessioned2015-12-13T22:27:40Z
dc.identifier.issn0022-1120
dc.identifier.urihttp://hdl.handle.net/1885/74045
dc.description.abstractRecent results have shown that convection forced by a temperature gradient along one horizontal boundary of a rectangular domain at a large Rayleigh number can be turbulent in parts of the flow field. However, the conditions for onset of turbulence, the dependence of flow and heat transport on Rayleigh number, and the roles of large and small scales in the flow, have not been established. We use three-dimensional direct numerical simulation (DNS) and large-eddy simulation (LES) over a wide range of Rayleigh numbers, Ra ~ 10 8-1015, for Prandtl number Pr = 5 and a small aspect ratio, and show that a sequence of several stability transitions at Ra ~ 10 10 - 1011 defines a change from laminar to turbulent flow. The Prandtl number dependence too is examined at Ra = 5.86 × 10 11. At the smallest Ra considered the thermal boundary layer is characterized by a balance of viscous stress and buoyancy, whereas inertia and buoyancy dominate in the large-Ra regime. The change in the momentum balance is accompanied by turbulent enhancement of the overall heat transfer, although both laminar and turbulent regimes give Nu ~ Ra1/5. The results support both viscous and inviscid theoretical scaling models from previous work. The mechanical energy budget for an intermediate range of Rayleigh numbers above onset of instability (1010 < Ra < 1013) reveals that the small scales of motion are produced predominantly by thermal convection, whereas at Ra ≥ 1014 shear instability of the large-scale flow begins to play a dominant role in sustaining the small-scale turbulence. Extrapolation to ocean conditions requires knowledge of the inertial regime identified here, but the simulations show that the corresponding asymptotic balance has not been fully realized by Ra ~ 1015.
dc.publisherCambridge University Press
dc.sourceJournal of Fluid Mechanics
dc.titleStability transitions and turbulence in horizontal convection
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume751
dc.date.issued2014
local.identifier.absfor040403 - Geophysical Fluid Dynamics
local.identifier.absfor020303 - Fluid Physics
local.identifier.ariespublicationU3488905xPUB3942
local.type.statusPublished Version
local.contributor.affiliationGayen, Bishakhdatta, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationGriffiths, Ross, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationHughes, Graham, College of Physical and Mathematical Sciences, ANU
local.description.embargo2037-12-31
local.bibliographicCitation.startpage698
local.bibliographicCitation.lastpage724
local.identifier.doi10.1017/jfm.2014.302
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
dc.date.updated2015-12-11T08:33:38Z
local.identifier.scopusID2-s2.0-84904060085
local.identifier.thomsonID000337925000029
CollectionsANU Research Publications

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