Flow regimes in T-shaped micro-mixers

tThe different flow regimes occurring in T-mixers are investigated by means of direct numerical simula-tions. Three different values of the aspect ratio of the inlet channels, i, that is their width to height ratioare considered, namely i= 0.75, 1 and 2. For the configurations with i= 0.75 and 1, the same behavioras previously described in the literature, is found. In particular, as the Reynolds number is increased, theflow evolves from vortical to engulfment steady regimes, then to unsteady asymmetric and symmetricperiodic regimes, until, finally, it becomes chaotic. All the critical values of the Reynolds number, at whichthe transitions between the different regimes occur, are found to be very similar for i= 0.75 and 1, whilesome differences are highlighted in the vorticity dynamics and characteristic frequencies of the unsteadyregimes. The observed scenario is completely different for i= 2. Indeed, in this case, the flow evolvesdirectly from the vortical regime to an unsteady symmetric behavior, with a vorticity dynamics that issignificantly different from those observed for the other aspect ratios.