Unsteady flow features in a T-shaped micro-mixer

A Direct Numerical Simulation of the mixing process between two water streams in a T-shaped micro-device indicates that for a certain range of Reynolds numbers the flow regime might be unsteady, with time-periodic structures. Pulsating flows strongly enhance the degree of mixing, that can be as large as twice the one that is observed in the steady engulfment regime. Then, when we increase the Reynolds numbers beyond the pulsating range, the flow is no more unsteady, with a consequent reduction of the mixing efficiency. In addition, we also observe that for our investigated geometry the unsteady, periodic behavior does not occur when the inlet flows are blunt and not fully developed.