Flow states in two-dimensional Rayleigh-Bénard convection as a function of aspect-ratio and Rayleigh number

Poel, E.P. van der; Stevens, R.J.A.M.; Sugiyama, K.; Lohse, D.

doi:10.1063/1.4744988

Publication 19 · Thermal convection

Flow states in two-dimensional Rayleigh-Bénard convection as a function of aspect-ratio and Rayleigh number

E.P. van der Poel, R.J.A.M. Stevens, K. Sugiyama, D. Lohse, Phys. Fluids 24, 085104 (2012).

Main finding

Flow-state selection can mimic scaling changes and remain relevant even when integral width effects appear small. The evidence is limited to two-dimensional simulations with mixed Prandtl and Rayleigh numbers across sweeps; it does not establish a universal critical aspect ratio, ultimate-regime scaling, three-dimensional thresholds, or a unique causal role for corner rolls.

Compensated Nusselt and Reynolds numbers against Rayleigh number for six aspect ratios — **How to read the figure.** Nusselt number (a) and Reynolds number (b) compensated by Ra^0.30, against Rayleigh number, for six aspect ratios in two-dimensional convection. The curves jump between branches as the flow reorganises into a different number of rolls. Those jumps look like changes of scaling exponent but are changes of flow state, so an exponent fitted across a branch jump does not mean what it appears to. Open the full-resolution figure. Figure 1. E.P. van der Poel et al. (2012). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

Persistent roll-state selection changes heat transport and can mimic aspect-ratio scaling transitions in two-dimensional convection.

Research context

The evidence is confined to two-dimensional simulations with mixed Prandtl and Rayleigh numbers across the sweeps. It does not establish a universal critical aspect ratio, an ultimate-regime transition, or three-dimensional thresholds.

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