Author
Winchester, P
Ntallas, V
Howell, P
Journal title
Physical Review Fluids
DOI
10.1103/PhysRevFluids.6.033502
Volume
6
Last updated
2021-10-19T13:24:10.75+01:00
Abstract
Using long-time direct numerical simulations, we analyse the reversals of the large scale zonal
flow in two-dimensional Rayleigh–B´enard convection with a rectangular geometry of aspect ratio Γ.
We impose periodic and free-slip boundary conditions in the streamwise and spanwise directions,
respectively. As Rayleigh number Ra increases, large scale flow dominates the dynamics of a moderate Prandtl number fluid. At high Ra, transitions are seen in the probability density function
(PDF) of the largest scale mode. For Γ = 2, the PDF first transitions from a Gaussian to a trimodal
behaviour, signifying the emergence of large scale flow reversals, where the flow fluctuates between
three distinct states: two states in which a zonal flow travels in opposite directions and one state
with no zonal mean flow. Further increase in Ra leads to a transition from a trimodal to a unimodal
PDF which demonstrates the disappearance of the zonal flow reversals. On the other hand, for
Γ = 1, the zonal flow reversals are characterised by a bimodal PDF of the largest scale mode, where
the flow fluctuates only between two distinct states with zonal flow travelling in opposite directions.
Symplectic ID
1168833
Favourite
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Publication type
Journal Article
Publication date
22 Mar 2021
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