Effect of confinement on global heat transfer scaling in Rayleigh-Bénard convection

Abstract eng:
We present the results from direct numerical simulations of Rayleigh-B´enard (RB) convection of Rayleigh number 106 ≤ Ra ≤ 1010 , Prandtl number 4.38 and width-to-height aspect ratio 1/32 ≤ Γ ≤ 1. Our results suggest that the power law is more rational to be fitted conditionally according to the three regimes classified by Chong et al.[1] as they are under different physical mechanisms on heat transfer. For instance, in regime II heat transport is accomplished by a single, or a few, system-sized plume(s), whereas in regime I it is carried out by fragmented plumes. Therefore, in contrast to RB flow at Γ = 1 (in the explored Ra range), there is no pure power-law scaling between Nusselt number N u and Ra whenever the convective state straddles over different regimes.

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