Mixing performance of arrow-shaped micro-devices

The process of liquid laminar mixing in arrow-shaped micro-devices is studied by direct numerical simulations. Two different CFD codes, i.e. Fluent (based on finite volume method) and Nek5000 (based on spectral element method) have been used to investigate the flow and concentration fields. Unexpectedly we observe that within the engulfment regime, the degree of mixing first increases and then diminishes as the inlet flow rate is increased. Such reduction in the degree of mixing, not observed in T-shaped mixers, can be imputed to the presence of a strong vortical structure at the center of the mixing channel. This result is important for control operations, as it shows that on one hand arrow type mixers are characterized by higher degree of mixing with respect to T-shaped mixers, but on the other hand they present a narrower range of optimal conditions.