Issue
EPL
Volume 87, Number 4, August 2009
Article Number 44006
Number of page(s) 6
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
DOI http://dx.doi.org/10.1209/0295-5075/87/44006
Published online 15 September 2009
EPL, 87 (2009) 44006
DOI: 10.1209/0295-5075/87/44006

Transition on local temperature fluctuations in highly turbulent convection

F. Gauthier1, J. Salort1, O. Bourgeois1, J.-L. Garden1, R. du Puits2, A. Thess2 and P.-E. Roche1

1   Institut Néel, CNRS/UJF - BP 166, F-38042 Grenoble cedex 9, France, EU
2   Technische Universität Ilmenau - Ehrenbergstraße 29, D-98693 Ilmenau, Germany, EU


received 15 April 2009; accepted in final form 13 August 2009; published August 2009
published online 15 September 2009

Abstract
In 1997, a new turbulent regime has been observed in a Rayleigh-Bénard 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.

PACS
47.27.te - Turbulent convective heat transfer.
44.25.+f - Heat transfer: Natural convection.
47.80.-v - Instrumentation and measurement methods in fluid dynamics.

© EPLA 2009