Analysis and multi-criteria design optimization of geometric characteristics of grooved micromixer

Computational fluids dynamics (CFDs) and numerical optimization techniques are applied in an integrated methodology to explore the effects of different geometric characteristics on fluid mixing in a staggered herringbone micromixer (SHM). To quantify the mixing intensity in the mixer a mixing index is defined on the basis of the intensity of segregation of the mass concentration on a cross-section plane in the mixing channel. Four geometric parameters, i.e., aspect ratio of the mixing channel, ratio of groove depth to channel height, ratio of groove width to groove pitch and the asymmetry factor (offset) of groove, are the design variables initially selected for optimization, then two more parameters, i.e., angle of the groove and number of grooves per channel section, are evaluated. The whole optimization is conducted with a multi-objective approach for which the mixing index at the outlet section and the pressure drop in the mixing channel are the performance criteria used as objective functions. The Pareto front of designs with the optimum trade-off, maximum mixing index with minimum pressure drop, is obtained.