Mixing Enhancement in Serpentine Micromixers with a Non-Rectangular Cross-Section

Abstract

In this numerical study, a new type of serpentine micromixer involving mixing units with a non-rectangular cross-section is investigated. Similar to other serpentine/spiral shaped micromixers, the design exploits the formation of transversal vortices (Dean flows) in pressure-driven systems, associated with the centrifugal forces experienced by the fluid as it is confined to move along curved geometries. In contrast with other previous designs, though, the use of non-rectangular cross-sections that change orientation between mixing units is exploited to control the center of rotation of the transversal flows formed. The associated extensional flows that thus develop between the mixing segments complement the existent rotational flows, leading to a more complex fluid motion. The fluid flow characteristics and associated mixing are determined numerically from computational solutions to Navier–Stokes equations and the concentration-diffusion equation. It is found that the performance of the investigated mixers exceeds that of simple serpentine channels with a more consistent behavior at low and high Reynolds numbers. An analysis of the mixing quality using an entropic mixing index indicates that maximum mixing can be achieved at Reynolds numbers as small as 20 in less than four serpentine mixing units.

Editorial for the Special Issue on Passive Micromixers

“…The numerical results showed a good agreement with a previously published experiment, with improved mixing performance compared to a simple serpentine channel. A similar investigation of flow and mixing in serpentine channels with a non-rectangular cross-section was conducted by Clark et al [2]. The results indicate enhancement in mixing performance using non-rectangular cross-section serpentine 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.…”

Mixing Optimization in Grooved Serpentine Microchannels

“…The centrifugal forces that are experienced by the fluid lead to the formation of transversal vortices [17], which can be exploited to intermix the fluid components of interest. At Reynolds numbers below 100, two vertically stacked vortices are formed, although more complex flow geometries can be achieved by operating at higher Reynolds numbers [17], or by using geometrical modifications such as surface patterns [46], modulation of the side walls [47], misaligned inlets [48], unbalanced sub-channels [49], non-rectangular cross-sections [50], or three-dimensional turns [51]. The second geometrical topology ( Figure 1b) uses an array of slanted V-shaped asymmetric groove-ridge patterns placed on the bottom [32,40], or top and bottom [48] of the channel.…”

Inertial Micromixing in Curved Serpentine Micromixers with Different Curve Angles

“…Akgönül et al investigated the micromixing performance of a symmetric and an asymmetric curvilinear microchannel having curve angle of 280 • for Reynolds numbers below 60 [26]. Clark et al numerically studied passive mixing in serpentine curved channels with curve angle of 180 • having non-circular cross-sections [27].…”