Mixing enhancement in a passive micromixer with convergent–divergent sinusoidal microchannels and different ratio of amplitude to wave length

Experimental investigations and computational fluid dynamic on the characteristics of mixing inside the fabricated micromixers have been conducted. In order to study the mixing, several micromixer made by CO2 laser ablation process with sinusoidal convergent–divergent cross section including the T-shape inlet have been employed. The fluid mixing is clearly observed using a digital microscope imaging system. Beside, computational fluid dynamics via finite element method is used for 3D modeling of single phase flow in a microchannel. Experimental results demonstrated the reasonable agreement with those obtained by CFD. The main purpose of this modeling is to extend the previous knowledge related to the Dean and separation vortices forming inside the convergent–divergent sinusoidal microchannels. Moreover, effects of designing parameters such as aspect ratio of cross section and ratio of amplitude to wave length (A/ʎ) and operational condition such as Reynolds number on pressure-drop and mixing index are also investigated. Therefore, based on the obtained results, best mixing condition at short mixing length is introduced and a new micromixer is suggested that may be considered as a proper case due to higher mixer index and ease of fabrication in comparison with previous ones used in biomedical and biochemical analysis.