Rotating turbulence under "precession-like" perturbation

TL;DR

This study investigates how changing the rotation axis in turbulent flows affects energy transfer, revealing that sudden changes can suppress inverse cascades and promote isotropic-like large-scale structures.

Contribution

It provides the first direct numerical simulation analysis of rotating turbulence under precession-like perturbations, highlighting the impact on energy cascades and flow structures.

Findings

Sudden axis change leads to dominant inverse energy cascade.

Regular axis changes suppress inverse cascade, favoring forward transfer.

Flow structures resemble isotropic turbulence under recurrent axis perturbations.

Abstract

The effects of changing the orientation of the rotation axis on homogeneous turbulence is considered. We perform direct numerical simulations on a periodic box of $1024^3$ grid points, where the orientation of the rotation axis is changed (a) at a fixed time instant (b) regularly at time intervals commensurate with the rotation time scale. The former is characterized by a dominant inverse energy cascade whereas in the latter, the inverse cascade is stymied due to the recurrent changes in the rotation axis resulting in a strong forward energy transfer and large scale structures that resemble those of isotropic turbulence.