# 1/f noise and long-term memory of coherent structures in a turbulent shear flow

## TL;DR

This study investigates 1/f noise and long-term memory in turbulent shear flow of liquid metal, revealing how symmetry breaking influences flicker noise characteristics and the flow's reversal dynamics.

## Contribution

It demonstrates the relationship between flow symmetry, 1/f noise, and power-law distributions of reversal waiting times in turbulent shear flow.

## Key findings

- 1/f^eta$ power-law spectra observed at high Reynolds numbers.
- Exponents $eta$ and $eta$ controlled by flow symmetry.
- Transition between different flicker noise types as symmetry is broken.

## Abstract

A shear flow of liquid metal (Galinstan) is driven in an annular channel by counter-rotating traveling magnetic fields imposed at the endcaps. When the traveling velocities are large, the flow is turbulent and its azimuthal component displays random reversals. Power spectra of the velocity field exhibit a $1/f^\alpha$ power law on several decades and are related to power-law probability distributions $P(\tau)\sim\tau^{-\beta}$ of the waiting times between successive reversals. This $1/f$ type spectrum is observed only when the Reynolds number is large enough. In addition, the exponents $\alpha$ and $\beta$ are controlled by the symmetry of the system : a continuous transition between two different types of Flicker noise is observed as the equatorial symmetry of the flow is broken, in agreement with theoretical predictions.