Análise de um micromixer passivo rômbico de colisões desequilibradas com subcanais deslocados

Abstract

In this work, we numerically analyze the mixing capabilities of a new type of planar passive micromixer, which uses unbalanced collisions promoted by asymmetrical subchannels with sudden displacements. The Navier-Stokes equations, the continuity equation and the diffusion-convection equation were solved using the finite element method. Among the boundary conditions used, seven different flows were tested, varying the Reynolds number from 5 to 100. The main characteristic of the proposed models is the adoption of a displacement in the widest of the asymmetrical subchannels. These displacements have constrictions that alter the velocity field, generating faster flow lines and secondary vortices. These hydrodynamic structures can increase the contact area between two fluids, favoring their mixing by accelerating the diffusion process. Three models of micromixers were proposed, where each micromixer has a different displacement following a rule of proportion. The mixing index, which is a parameter used to measure the efficiency of micromixers, and the pressure drop for each case were calculated and analyzed. The simulations showed that the displacements generated expansion vortices and modified the unbalanced shock in the recombination zones of the micromixers, promoting Chaotic Advection. All three proposed models, 𝑊𝑟 0.5, 𝑊𝑟 1.0 and 𝑊𝑟 2.0, obtained higher efficiencies than the reference model in all 𝑅𝑒 except for 𝑅𝑒 100. For lower, medium, and higher Reynolds numbers, the 𝑊𝑟 2.0, 𝑊𝑟 1.0 and 𝑊𝑟 0.5 micromixers showed the highest efficiencies, respectively, with 𝑊𝑟 0.5 achieving an 85% mixing at 𝑅𝑒 100. While 𝑊𝑟 0.5 had the lowest pressure drops, 𝑊𝑟 2.0 got the highest due to tighter displacements.