English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present measurements of the orientation $\theta_0$ and temperatureamplitude $\delta$ of the large-scale circulation in a cylindrical sample ofturbulent Rayleigh-Benard convection (RBC) with aspect ratio $\Gamma \equiv D/L= 1.00$ ($D$ and $L$ are the diameter and height respectively) and for thePrandtl number $Pr \simeq 0.8$. Results for $\theta_0$ revealed a preferredorientation with upflow in the West, consistent with a broken azimuthalinvariance due to Earth's Coriolis force [see \cite{BA06b}]. They yielded theazimuthal diffusivity $D_\theta$ and a corresponding Reynolds number$Re_{\theta}$ for Rayleigh numbers over the range $2\times 10^{12} < Ra <1.5\times 10^{14}$. In the classical state ($Ra < 2\times 10^{13}$) the resultswere consistent with the measurements by \cite{BA06a} for $Ra < 10^{11}$ and$Pr = 4.38$ which gave $Re_{\theta} \propto Ra^{0.28}$, and with thePrandtl-number dependence $Re_{\theta} \propto Pr^{-1.2}$ as found previouslyalso for the velocity-fluctuation Reynolds number $Re_V$ \cite[]{HGBA15b}. Atlarger $Ra$ the data for $Re_{\theta}(Ra)$ revealed a transition to a newstate, known as the "ultimate" state, which was first seen in the Nusseltnumber $Nu(Ra)$ and in $Re_V(Ra)$ at $Ra^*_1 \simeq 2\times 10^{13}$ and$Ra^*_2 \simeq 8\times 10^{13}$. In the ultimate state we found $Re_{\theta}\propto Ra^{0.40\pm 0.03}$.  Recently \cite{SU15} claimed that non-Oberbeck-Boussinesq effects on theNusselt and Reynolds numbers of turbulent RBC may have been interpretederroneously as a transition to a new state. We demonstrate that their reasoningis incorrect and that the transition observed in the G\"ottingen experimentsand discussed in the present paper is indeed to a new state of RBC referred toas "ultimate".

journal of fluid mechanics

Azimuthal diffusion of the large-scale-circulation plane, and absence of  significant non-Boussinesq effects, in turbulent convection near the  ultimate-state transition