Transition on local temperature fluctuations in highly turbulent convection

Frédéric Gauthier (1) , Julien Salort (1) , Olivier Bourgeois (2) , Jean-Luc Garden (3) , Ronald Du Puits (4) , Andre Thess (4) , Philippe-Emmanuel Roche (1)

1 NEEL - HELFA - Hélium : du fondamental aux applications
2 NEEL - TPS - Thermodynamique et biophysique des petits systèmes
3 NEEL - Institut Néel
4 TU - Technische Universität Ilmenau

In 1997, a new turbulent regime has been observed in a Rayleigh-B'enard cell and has been interpreted as the "Ultimate Regime" of convection. This observation was based on global heat transfer measurements at very high Rayleigh numbers (Ra). Using a set-up similar to the one used in 1997, we examine the signature of this regime from within the flow itself. A systematic study of probe-size corrections shows that the earlier local temperature measurements within the flow were altered by an excessive size of thermometer, but not according to a theoretical model proposed in the literature. Using a probe one order of magnitude smaller than the one used previously, we find evidence that the transition to the very-high-Ra regime is indeed accompanied with a clear change in the statistics of temperature fluctuations in the flow

Domaines: Autre [cond-mat.other]; Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Frédéric Gauthier, Julien Salort, Olivier Bourgeois, Jean-Luc Garden, Ronald Du Puits, et al.. Transition on local temperature fluctuations in highly turbulent convection. EPL - Europhysics Letters, 2009, 87, pp.44006. ⟨10.1209/0295-5075/87/44006⟩. ⟨hal-00384943⟩