Sorting prolate and oblate spheroids with a diatomic gas in a magnetic field

TL;DR

This paper investigates how magnetic fields influence the sedimentation and separation of prolate and oblate spheroids in a diatomic gas, revealing the role of anisotropic odd viscosities due to the Senftleben-Beenakker effect.

Contribution

It provides a theoretical analysis of spheroid sorting in a magnetic field considering anisotropic odd viscosities caused by the Senftleben-Beenakker effect.

Findings

For large magnetic fields, odd viscosities are opposite in sign.

Oblate and prolate spheroids can be separated via sedimentation.

The forces depend on spheroid shape and magnetic field strength.

Abstract

For a gas of diatomic particles with a nonzero magnetic moment, the Senftleben-Beenakker effect says that transport can be affected by a magnetic field even when the particles are neutral. As a consequence of the Senftleben-Beenakker effect, two anisotropic odd viscosities become nonvanishing which for large magnetic field are of opposite sign. We solve for the anisotropic odd viscous Stokes flow around the spheroid using the Lorentz reciprocal theorem and show that the forces on oblate and prolate spheroids are such that they can be separated upon undergoing sedimentation in a diatomic gas with a background magnetic field.