Mixing and separation of two-fluid flow in a micro planar serpentine channel

Numerical simulation, micro-fabrication and flow visualization were performed for a micro planar serpentine channel to reveal the mixing and separation characteristics of two fluid streams with or without density variation. When the densities of the injected fluids are equal, the induced vortices laminate the interface and considerably increase the interfacial area in a spiral manner. It compensates the negative effect of the short residence period of fast flow for mixing. When the densities of the injected fluids slightly differ, the denser fluid distributes in regions of the outer corner of turning. Separation is the effect resulting from a density difference and a velocity difference in a flow field that can be promoted on flowing in a serpentine channel with a relatively rapid bulk flow. The design of a channel incorporating an alternation of cross-sectional areas improves the velocity difference. This hypothesis is verified by both numerical simulation and experimental observation. A green dye (density 2030 kg m−3) is separated from deionized water (density 1000 kg m−3) and double interfaces are formed significantly under conditions of flow in a micro planar serpentine channel at Reynolds number 16.