Effect of helicity and rotation on the free decay of turbulent flows

TL;DR

This study investigates how helicity and rotation influence the decay of turbulent energy, revealing that helicity significantly affects decay rates in rotating flows due to changes in energy and helicity cascades.

Contribution

It demonstrates the impact of helicity on energy decay in rotating turbulence, highlighting differences in cascade processes and flow structures compared to non-helical cases.

Findings

Helicity affects decay rates in rotating turbulence.

Rotation alters energy and helicity cascade dynamics.

Flow structures differ at late times based on helicity content.

Abstract

The self-similar decay of energy in a turbulent flow is studied in direct numerical simulations with and without rotation. Two initial conditions are considered: one non-helical (mirror-symmetric), and one with maximal helicity. The results show that, while in the absence of rotation the energy in the helical and non-helical cases decays with the same rate, in rotating flows the helicity content has a major impact on the decay rate. These differences are associated with differences in the energy and helicity cascades when rotation is present. Properties of the structures that arise in the flow at late times in each time are also discussed.