Reynolds number measurements for turbulent Rayleigh-B\'enard convection with $0.17 < Pr < 0.88$

We report Reynolds-number measurements from space-time cross-correlation functions of shadowgraph images taken of turbulent Rayleigh-B\'enard convection in a cylindrical cell of height $L = 9.5$ mm and aspect ratio $\Gamma = 10.6$. The fluids were pure gases with Prandtl-numbers $Pr\approx0.7$ and gas mixtures with $0.17 \leq Pr < 0.7$. The Rayleigh-number range was $10^{5} \leq Ra \leq 10^{8}$. The elliptic approximation of He and Zhang\footnote{G.-W. He and J.-B. Zhang, Phys. Rev. E, \textbf{73}, 055303 (2006).} was used to calculate the mean flow velocity $U$ and the rms fluctuation velocity $V$. For this system $U$ was close to zero, and the Reynolds number $Re_{V}$ based on $V$ had $Ra$- and $Pr$-dependences consistent with the Grossmann-Lohse model.\footnote{S. Grossmann and D. Lohse, Phys. Rev. E, \textbf{66}, 016305 (2002).}