Exploring the phase space of multiple states in highly turbulent Taylor-Couette flow

TL;DR

This study explores multiple turbulent flow states in highly turbulent Taylor-Couette flow, revealing their robustness, control by rotation ratio, complex phase space paths, and the discovery of an antisymmetrical roll state in larger aspect ratio setups.

Contribution

It demonstrates the existence and robustness of multiple turbulent states across a wide range of Taylor numbers, including new flow structures like the antisymmetrical roll state.

Findings

Multiple states are robust and likely persist beyond Ta=10^{13}.

Rotation ratio strongly controls flow state transitions.

Discovery of an antisymmetrical roll state in highly turbulent flow.

Abstract

We investigate the existence of multiple turbulent states in highly turbulent Taylor-Couette flow in the range of $\mathrm{Ta}=10^{11}$ to $9\cdot10^{12}$, by measuring the global torques and the local velocities while probing the phase space spanned by the rotation rates of the inner and outer cylinder. The multiple states are found to be very robust and are expected to persist beyond $\mathrm{Ta}=10^{13}$. The rotation ratio is the parameter that most strongly controls the transitions between the flow states; the transitional values only weakly depend on the Taylor number. However, complex paths in the phase space are necessary to unlock the full region of multiple states. Lastly, by mapping the flow structures for various rotation ratios in a Taylor-Couette setup with an equal radius ratio but a larger aspect ratio than before, multiple states were again observed. Here, they are characterized by even richer roll structure phenomena, including, for the first time observed in highly turbulent TC flow, an antisymmetrical roll state.