Exploring the origin of Turbulent Taylor rolls

TL;DR

This study investigates the formation and dynamics of large-scale Taylor rolls in turbulent Taylor-Couette flow through numerical simulations, revealing complex velocity couplings influenced by the Coriolis force.

Contribution

It provides new insights into the mechanisms behind turbulent Taylor roll formation and the effects of Coriolis forces in highly turbulent regimes.

Findings

Coriolis force induces one-way coupling in boundary layers

Bulk flow exhibits two-way velocity coupling

Differences observed compared to shear flows without boundary layers

Abstract

Since Taylor's seminal paper, the existence of large-scale quasi-axisymmetric structures has been a matter of interest when studying Taylor-Couette flow. In this manuscript, we probe their formation in the highly turbulent regime by conducting a series of numerical simulations at a fixed Reynolds number $Re_s=3.6\times 10^4$ while varying the Coriolis parameter to analyze the flow characteristics as the structures arise and dissipate. We show how the Coriolis force induces a one-way coupling between the radial and azimuthal velocity fields inside the boundary layer, but in the bulk there is a two-way coupling that causes competing effects. We discuss how this complicates the analogy of narrow-gap Taylor-Couette to other convective flows. We then compare these statistics to a similar shear flow without no-slip boundary layers, showing how this double coupling causes very different effects. We finish by reflecting on the possible origins of turbulent Taylor rolls.