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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

In this study, we combine experiments and direct numerical simulations toinvestigate the effects of the height of transverse ribs at the walls on bothglobal and local flow properties in turbulent Taylor-Couette flow. We createrib roughness by attaching up to 6 axial obstacles to the surfaces of thecylinders over an extensive range of rib heights, up to blockages of 25% of thegap width. In the asymptotic ultimate regime, where the transport isindependent of viscosity, we emperically find that the prefactor of the$Nu_{\omega} \propto Ta^{1/2}$ scaling (corresponding to the drag coefficient$C_f(Re)$ being constant) scales with the number of ribs $N_r$ and by the ribheight $h^{1.71}$. The physical mechanism behind this is that the dominantcontribution to the torque originates from the pressure forces acting on therib which scale with rib height. The measured scaling relation of $N_rh^{1.71}$ is slightly smaller than the expected $N_r h^2$ scaling, presumablybecause the ribs cannot be regarded as completely isolated but interact. In thecounter-rotating regime with smooth walls, the momentum transport is increasedby turbulent Taylor vortices. We find that also in the presence of transverseribs these vortices persist. In the counter-rotating regime, even for largeroughness heights, the momentum transport is enhanced by these vortices.

Rough wall turbulent Taylor-Couette flow: the effect of the rib height