Passive scalar cascades in rotating helical and non-helical flows

TL;DR

This paper investigates how helicity influences the passive scalar spectrum in rotating turbulent flows, revealing different scaling laws and proposing a phenomenological model to explain these effects.

Contribution

It provides new insights into the impact of helicity on passive scalar spectra in rotating turbulence through numerical simulations and a phenomenological model.

Findings

Passive scalar spectrum is shallower in rotating helical flows.

Scaling laws differ between helical and non-helical flows.

A phenomenological model links helicity effects to energy and scalar spectra.

Abstract

We study how helicity affects the spectrum of a passive scalar in rotating turbulent flows, using numerical simulations of turbulent flows with or without rotation, and with or without injection of helicity. Scaling laws for energy and passive scalar spectra in the direction perpendicular to the rotation axis differ in rotating helical flows from the ones found in the non-helical case, with the spectrum of passive scalar variance in the former case being shallower than in the latter. A simple phenomenological model that links the effects of helicity on the energy spectrum with the passive scalar spectrum is presented.