Viscous tilting and production of vorticity in homogeneous turbulence

TL;DR

This paper reveals that viscous effects in turbulence not only destroy vorticity but can also locally generate and reorient vorticity through viscous tilting, challenging traditional views.

Contribution

It demonstrates, using experimental and numerical data, that viscous effects actively produce and tilt vorticity, not just dissipate it, in homogeneous turbulence.

Findings

Viscous effects can locally produce vorticity.

Viscous tilting influences vorticity orientation.

Viscous effects are as important as vortex stretching.

Abstract

Viscous depletion of vorticity is an essential and well known property of turbulent flows, balancing, in the mean, the net vorticity production associated with the vortex stretching mechanism. In this letter we however demonstrate that viscous effects are not restricted to a mere destruction process, but play a more complex role in vorticity dynamics that is as important as vortex stretching. Based on results from particle tracking experiments (3D-PTV) and direct numerical simulation (DNS) of homogeneous and quasi isotropic turbulence, we show that the viscous term in the vorticity equation can also locally induce production of vorticity and changes of its orientation (viscous tilting).