Intermittent flow behavior in experimental Taylor-Couette flow described by exact coherent structures

A dynamical systems approach to understanding turbulence suggests that the complicated motion of the flow is shaped by special solutions to the Navier-Stokes equations known as exact coherent structures (ECS). In this picture, turbulent flow co-evolves with, or "shadows", one such solution for a time; then a different ECS; and so on. This qualitative picture has recently been confirmed quantitatively at certain Reynolds numbers in experimental turbulent Taylor-Couette flow. Here we apply a similar methodology to an experimental Taylor-Couette flow that has the property of intermittency, wherein the flow exhibits a high degree of regularity for certain intervals punctuated at other times by significant increase in spatial and temporal variation of the flow. We show that this behavior is due to the dominance of a handful of less unstable ECSs during certain intervals, while more unstable ECSs dominate the more active regions of the flow.