Numerical investigation of multi-scale mixing in microchannel T-junction with wavy structure

Mixing in chemical microreactors is a multi-scale processes as the transport mechanisms occur at different length scales. The small scale mixing depends mainly on molecular diffusion which causes conventional microchannel T-junction has poor mixing quality. To improve the quality, one can utilize secondary flow generated by wavy structure to enhance chaotic mixing. To gain better understanding of the interplay of transport mechanism, we develop numerical model for mixing in micro-channel T-junction with wavy structure. To ensure robust and accurate solutions, several discretization methods and mesh sizes were tested and compared. It is found that the solutions are sensitive to the Reynolds; huge amount of mesh (>10⁷) is required to resolve small molecular diffusion and chaotic mixing especially at high Schmidt number, whilst relatively lesser mesh is found to be sufficient for conventional T-junction. Further, parallelization is found to be beneficial to expedite the computation, albeit the speed is not linear with the number of the processors. The mixing quality of T-junction with wavy structure is then compared with that of conventional T-junction counterpart. It is noted that up to 50% improvement of mixing quality is achieved with wavy structure which has potential for several applications.