title: Prandtl and Rayleigh number dependence of the Reynolds number in turbulent thermal convection.
abstract: The Prandtl and Rayleigh number dependences of the Reynolds number in turbulent thermal convection following from the unifying theory by Grossmann and Lohse [J. Fluid Mech. 407, 27 (2000); Phys. Rev. Lett. 86, 3316 (2001)] are presented and compared with various recent experimental findings. This dependence Re(Ra,Pr) is more complicated than a simple global power law. For Pr=5.5 and 10(8)<Ra<10(10) the effective or local power law exponent of Re as a function of Ra is definitely less than 0.50, namely, Re approximately Ra(0.45), in agreement with Qiu and Tong's experimental findings [Phys. Rev. E 64, 036304 (2001)]. We also calculated the kinetic boundary layer width. Both in magnitude and in Ra scaling it is consistent with the data.
authors.affiliation: Department of Physics, University of Marburg, Renthof 6, D-35032 Marburg, Germany. grossmann@physik.uni-marburg.de
authors.forename: Siegfried
authors.initials: S
authors.lastname: Grossmann
authors.forename: Detlef
authors.initials: D
authors.lastname: Lohse