T-shaped micro-mixer: unsteady flow regimes

The flow in a T-mixer is characterized by different regimes, depending on the flow Reynolds number. When the Reynolds number is above a critical value, the flow is characterized by vortical structures which breaks the symmetry and enhances the mixing efficiency (engulfment).  When the Reynolds number is further increased, the flow becomes unsteady, yielding to a boost of the mixing efficiency.

Numerical simulations have been carried out and we found two different  unsteady regimes, depending on the Reynolds number. The first one (UAR), occurring at Re=220 remains asymmetric, while at a Reynolds number of about 400 the flow oscillates between a symmetric and asymmetric state (USR),  with a consequential detriment of the mixing efficiency.

We  also characterize the first regime with a 3D stability analysis, investigating the effect of the inlet conditions on the onset of the instability.

Related publications:

Andrea Fani, Simone Camarri, Maria Vittoria Salvetti: Unsteady asymmetric engulfment regime in a T-mixer. In: Physics of Fluids, 26 , pp. 074101, 2014, ISSN: 1070-6631.