Winchester, P
Ntallas, V
Howell, P
Journal title
Physical Review Fluids
Last updated
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
Publication type
Journal Article
Publication date
22 Mar 2021
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