The Stuart number (N), also known as magnetic interaction parameter, is a dimensionless number of fluids, i.e. gases or liquids.
It is named after mathematician John Trevor Stuart.
[1] It is defined as the ratio of electromagnetic to inertial forces, which gives an estimate of the relative importance of a magnetic field on a flow.
The Stuart number is relevant for flows of conducting fluids, e.g. in fusion reactors, steel casters or plasmas.
[2]