Exploring the magnetic manipulation of gases

To control gas mixtures with magnets, researchers must exploit the magnetic properties of gas species. However, the effects of magnetic fields on gas transport are not well explored. In particular, few studies have focused on how magnets affect differential diffusion, in which different chemical species diffuse at different rates within a mixture.

Kruse et al. demonstrated that magnetic fields can be used to manipulate the mixing of gases, and then quantified the conditions needed to achieve the desired gas transport effects. The authors used numerical simulations in a computational fluid dynamics framework to investigate a mixture of nitrogen gas and oxygen gas with a composition representative of air. Oxygen and nitrogen exhibit large differences in magnetic susceptibility: Oxygen is attracted to a magnetic field, whereas nitrogen is weakly repelled.

The authors measured the timescale and magnitude of the oxygen separation from nitrogen for various densities of the mixture and intensities of the magnetic field. They found that different initial gradients of species composition play a key role in the formation of sustained flow structures and the resulting mixing dynamics.

“With this fundamental study, we suggest a new means to control gas mixtures, paving the way for novel technologies in a wide range of applications, from clean engines to chemical processes,” said author Alexander Kruse. “This is the beginning of a research journey towards application to practical systems.”

For example, magnetic forces could be used to locally enhance oxygen concentration in engineering systems utilizing air.

Next, the authors plan to experimentally validate these results by mixing the gases in a purpose-built rig, as well as further study how gradients in magnetic susceptibility affect the dynamics of a gas mixture.

Source: “Numerical investigation of the effect of a magnetic field on the transport of oxygen in air,” by A. C. Kruse, P. G. Aleiferis, and A. Giusti, Physics of Fluids (2026). The article can be accessed at https://doi.org/10.1063/5.0319017 .