Modelling annular micromixers

Magnetohydrodynamic mixing of two fluids in an annular microchannel is modelled as a two-dimensional laminar convection-diffusion problem and examined using asymptotic analysis and numerical simulation. The time T required for mixing of a plug of solute depends on the Peclet number Pe and on the geometry of the annulus. Three scaling regimes are identified: purely diffusive, Taylor-dispersive, and convection-dominated; each has a characteristic power-law dependence of T upon Pe. Consequences of these results for optimal micromixer design are discussed.