Entropic Evaluation of Dean Flow Micromixers

In the present work, we investigate computationally, using COMSOL Multiphysics and its CFD and Chemical Species Transport modules, the use of spiral channels at Reynolds numbers from 25 to 900, as mixing structures. In this system the centrifugal forces experienced by the fluid as it travels along the curved trajectory, induce counter-rotating flows (Dean vortices). The presence of these transversal flows promotes the mixing of chemical species which are introduced in the system at different positions across the section of the channel. The COMSOL Multiphysics allows for the simultaneous solving of the Navier – Stokes equations for the fluid flow and the diffusion – convection equations for the concentration of chemical species. Concentration images obtained at different position along the channel are used to evaluate the mixing efficiency using a measure based on the Shannon entropy. We have previously found this measure to be useful in understanding mixing in mixers similar with the staggered herringbone type.