On the inverse energy transfer in rotating turbulence

TL;DR

This paper investigates the mechanisms behind inverse energy transfer in rotating turbulence, revealing that three-dimensional modes, especially homochiral channels, significantly contribute alongside two-dimensional modes.

Contribution

It demonstrates through simulations that 3D modes play a crucial role in inverse energy transfer, challenging the view that it is solely due to 2D modes.

Findings

2D modes are essential for stationary inverse cascade.

3D modes, particularly homochiral channels, also transfer energy upscale.

Removing 2D modes disrupts but does not eliminate inverse transfer.

Abstract

Rotating turbulence is an example of a three-dimensional system in which an inverse cascade of energy, from the small to the large scales, can be formed. While usually understood as a byproduct of the typical bidimensionalization of rotating flows, the role of the three-dimensional modes is not completely comprehended yet. In order to shed light on this issue, we performed direct numerical simulations of rotating turbulence where the 2D modes falling in the plane perpendicular to rotation are removed from the dynamical evolution. Our results show that while the two-dimensional modes are key to the formation of a stationary inverse cascade, the three-dimensional degrees of freedom play a non-trivial role in bringing energy to the larger scales also. Furthermore, we show that this backwards transfer of energy is carried out by the homochiral channels of the three-dimensional modes.