Performance Analysis and Numerical Evaluation of Mixing in 3-D T-Shape Passive Micromixers

Abstract

In micromixer devices, laminar characteristics of the flow domain and small diffusion constants of the fluid samples that are mixed characterize the mixing process. The advection dominant flow and transport processes that develop in these devices not only create significant challenges for numerical solution of the problem, but they are also the source of numerical errors which may lead to confusing performance evaluations that are reported in the literature. In this study, the finite volume method (FVM) and finite element method (FEM) are used to characterize these errors and critical issues in numerical performance evaluations are highlighted. In this study, we used numerical methods to evaluate the mixing characteristics of a typical T-shape passive micromixer for several flow and transport parameters using both FEM and FVM, although the numerical procedures described are also equally applicable to other geometric designs as well. The outcome of the study shows that the type of stabilization technique used in FEM is very important and should be documented and reported. Otherwise, erroneous mixing performance may be reported since the added artificial diffusion may significantly affect the mixing performance in the device. Similarly, when FVM methods are used, numerical diffusion errors may become important for certain unstructured discretization techniques that are used in the idealization of the solution domain. This point needs to be also analyzed and reported when FVM is used in performance evaluation of micromixer devices. The focus of this study is not on improving the mixing performance of micromixers. Instead, we highlight the bench scale characteristics of the solutions and the mixing evaluation procedures used when FVM and FEM are employed.

Novel 3-D T-Shaped Passive Micromixer Design with Helicoidal Flows

“…where σ 2 , σ 2 max , c, c avg , u, and A denote variance, maximum variance, concentration, flowrate-averaged concentration on a cross-section, velocity, and area respectively. Dimensionless numbers, i.e., Reynolds (Re) and Peclet (Pe) are calculated in the mixing channel as described in the Reference [46]. While the turbulent or laminar behavior of the flow is defined by Re number, Pe number characterizes the advection or diffusion dominance in the transport.…”

“…Processes 2019, 7, x FOR PEER REVIEW 4 of 21 [46]. While the turbulent or laminar behavior of the flow is defined by Re number, Pe number characterizes the advection or diffusion dominance in the transport.…”

Editorial for the Special Issue on Passive Micromixers

“…The important areas being focused upon are the numerical and experimental analyses of flow and mixing in different micromixers [1,2,3,4,5], optimization [6,7,8], and fabrication of micromixers [9]. In the review paper [10], recent developments in both active and passive micromixers are summarized and discussed.…”

“…Computational fluid dynamics (CFD) analysis of flow and mixing is seen as an important tool in designing passive micromixers in eight research articles [1,2,3,4,5,6,7,8]. Javaid et al [1] proposed a serpentine-shaped micromixer with sinusoidal walls and conducted a CFD analysis using COMSOL Multiphysics software.…”

“…However, at a fixed flow rate, the mixing performance is superior in the case of electro-osmotic flow than pressure-driven flow. Okuducu and Aral [5] conducted a different study, which focused on the comparative evaluation of the finite volume method (FVM) and finite element method (FEM) to characterize numerical errors in mixing analysis. Using T-mixer geometry and two CFD tools, which were namely OpenFoam (FVM-based) and COMSOL Multiphysics (FEM-based), a detailed analysis based on mesh structure, orientation and flow parameters was presented.…”