Shot noise of thermal plumes : Evidence of a boundary layer instability consistent with the onset of Kraichnan's Regime of convection

Frédéric Gauthier (1) , Philippe-Emmanuel Roche (1)

1 NEEL - HELFA - Hélium : du fondamental aux applications

In 1997, an enhancement of heat transfer has been reported[PRL 79,3648 (1997)] in Rayleigh-Bénard convection for Rayleigh numbers Ra>10^12 . This new regime -named "Ultimate Regime" in the original paper- was interpreted as the regime predicted by Kraichnan in 1962 [Phys. Fluids 5,1374 (1962) ] and which is characterized by the turbulence of the boundary layers of the convection cell. Although this interpretation has been indirectly supported by specific experimental tests, including the observation of the Nu∼ Ra^1/2 scaling predicted by Kraichnan for asymptotically high Ra [PRE 63,045303(R) (2001)], a direct evidence of fluctuations in the boundary layer was still missing. We report such an observation based on the measurement of the shot-noise induced by thermal plumes in the heating plate [EPL 83,24005 (2008)].

Domaines: Autre [cond-mat.other]

Frédéric Gauthier, Philippe-Emmanuel Roche. Shot noise of thermal plumes : Evidence of a boundary layer instability consistent with the onset of Kraichnan's Regime of convection. 12th EUROMECH European Turbulence Conference, Sep 2009, Marburg, Germany. pp.521-524, ⟨10.1007/978-3-642-03085-7_125⟩. ⟨hal-00430193⟩