Numerical and experimental investigation of mixing characteristics in the constructal tree-shaped microchannel

The constructal tree-shaped configuration was presented for the application of rapid mixing of fluids in the microchannel, inspired by the geometry of biological tissues. Mixing characteristics of such configuration was investigated by computer simulation and was then supported experimentally. The Navier–Stokes equations were solved for the elementary T-junction structure, and three flow regimes were distinguished with the increase of Reynolds numbers, namely stratified, vortex and engulfment regimes. Due to the presence of secondary flow, the intertwinement of streamlines induced by the vortex flow causes decrease of the scale of segregation and the reduction of the diffusive distance in the mixing process. Variations of concentration distributions and mixing efficiencies along the mixing channel and with Reynolds number were analyzed and compared for the single, double, and triple T-shaped microchannels. The results showed that high mixing performance could be achieved even at relatively low Reynolds number by using the constructal tree-shaped structure. Furthermore, several tree-shaped microstructures were fabricated to conduct the verification experiments for numerical simulations. Numerical and experimental investigations indicated that the constructal tree-shaped structure, which consists of a large number of multi-T channels, is an excellent configuration for the micromixing.