Comment on "Turbulent heat transport near critical points: Non-Boussinesq effects" ( cond-mat/0601398 )

Xavier Chavanne (1) , Philippe-Emmanuel Roche (2) , Benoît Chabaud (2) , Bernard Hébral (2) , Francesca Chillà (3) , Bernard Castaing (3)

1 IPGP - Institut de Physique du Globe de Paris
2 CRTBT - Centre de Recherches sur les Très Basses Températures
3 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

In a recent preprint ( cond-mat/0601398 ), D. Funfschilling and G. Ahlers describe a new effect, that they interpret as non-Boussinesq, in a convection cell working with ethane, near its critical point. They argue that such an effect could have spoiled the Chavanne {\it et al.} (Phys. Rev. Lett. {\bf 79} 3648, 1997) results, and not the Niemela {\it et al.} (Nature, {\bf 404}, 837, 2000) ones, which would explain the differences between these two experiments. We show that:-i)Restricting the Chavanne's data to situations as far from the critical point than the Niemela's one, the same discrepancy remains.-ii)The helium data of Chavanne show no indication of the effect observed by D. Funfschilling and G. Ahlers.

Mots clés: Boussinesq effects; convection; ultimate regime

Domaines: Autre [cond-mat.other]

Xavier Chavanne, Philippe-Emmanuel Roche, Benoît Chabaud, Bernard Hébral, Francesca Chillà, et al.. Comment on "Turbulent heat transport near critical points: Non-Boussinesq effects" ( cond-mat/0601398 ). 2006. ⟨hal-00020417⟩