Flow reversals in turbulent convection with free-slip walls

Abstract

We perform numerical simulations of turbulent convection for infinite Prandtl number with free-slip walls, and study the dynamics of flow reversals. We show interesting correlations between the flow reversals and the nonlinear interactions among the large-scale flow structures represented by the modes $(1,1),(2,1),(3,1)$ and some others. After a flow reversal, the odd modes, e.g. $(1,1),(3,1)$, switch sign, but the even modes, e.g. $(2,2)$, retain their sign. The mixed modes $(1,2)$ and $(2,1)$ fluctuate around zero. Using the properties of the modes and their interactions, we show that they form a Klein four-group $Z_2\times Z_2$. We also show that for the free-slip boundary condition, the corner rolls and vortex reconnection are absent during a flow reversal, in contrast to active role played by them in flow reversals for the no-slip boundary condition. We argue that the flow reversals with the no-slip and free-slip boundary conditions are different because they are induced by nonlinearities $(\mathbf{u}\cdot \nabla )\mathbf{u}$ and $(\mathbf{u}\cdot \nabla )\theta$ respectively.

25 pages, 13 figures, accepted in Physics of Fluids

References in corpus (2)

• Rotations and cessations of the large-scale circulation in turbulent Rayleigh-Benard convection
• Dynamics of reorientations and reversals of large scale flow in Rayleigh-Benard convection

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• On the Applicability of Low-Dimensional Models for Convective Flow Reversals at Extreme Prandtl Numbers
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• Discrete Symmetries in Dynamo Reversals