Ultimate regime in Rayleigh–Bénard convection: The role of plates

Abstract

The ultimate regime of convection, long ago predicted by Kraichnan ͓Phys. Fluids 5, 1374 ͑1962͔͒, could be called elusive because some apparently equivalent experiments showed it while others did not, with no apparent reasons for this discrepancy. In this paper, we propose a model which accounts for the finite heat conductivity and heat capacity of real active boundaries. Bad thermal characteristics of the plates can explain differences between various experiments, in agreement with recent numerical simulations.

Thermal boundary layer near roughnesses in turbulent Rayleigh-Bénard convection: Flow structure and multistability

“…2 It is now clear however that the plates and the boundary conditions play a crucial role in the dynamics of the system. [3][4][5][6][7][8] To understand how instabilities develop near the plates and how they affect the general dynamics of heat transport, one approach is to purposely change the plate properties to trigger transitions in the boundary layers. One possibility is to introduce controlled plate roughnesses.…”

Comments on heat transfer efficiency in cryogenic helium turbulent Rayleigh-Bénard convection

“…Based on the numerical simulations of Verzicco (2004) and the experiments with water by Funfschilling, Brown, Nikolaenko & Ahlers (2005) and with SF6 by Ahlers, Funfschilling & Bodenschatz (2009) it is expected that finite conduction of plates will suppress the Nu values. Taking into account the dynamics of plumes, Chilla, Rastello, Chaumat & Castaing (2004) derived approximate criteria to account for the "plates effect". According to their "thin plates criterion" (which for our plates is more stringent than their "thick plates criterion"), the condition…”

Efficiency of Heat Transfer in Turbulent Rayleigh-Bénard Convection

“…(i) As already mentioned, our cell is designed to minimize sidewall and parasitic heat leak corrections; we do not expect any significant corrections due to finite conductivity of plates [17,18], and the measuring protocol is chosen to stay sufficiently away from the critical point. (ii) The quantitatively correct form for all these corrections, due to the complexity of the problem, is generally not known.…”