Unsteady flow regimes in arrow-shaped micro-mixers with different tilting angles

Two arrow-shaped micro-mixers, obtained from the classical T-shaped geometry by tilting downward the inlet channels, are considered herein. The two configurations, having different tilting angle values, have been chosen since they show significantly different flow topologies and mixing performances at low Reynolds numbers. In the present paper, we use both experimental flow visualizations and direct numerical simulations to shed light on the mixing behavior of the two configurations for larger Reynolds numbers, for which the mixers present unsteady periodic flows, although in laminar flow conditions. The tilting angle influences the flow dynamics also in the unsteady regimes and has a significant impact on mixing. The configuration characterized by the lower tilting angle, i.e., α = 10°, ensures a better global mixing performance than the one with the larger angle, i.e., α = 20°.