Numerical study on shape optimization of groove micromixers
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RESEARCH PAPER
Numerical study on shape optimization of groove micromixers Mranal Jain • Abhijit Rao • K. Nandakumar
Received: 18 December 2012 / Accepted: 4 March 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract The performance of a homogeneous T-mixer can be enhanced significantly by the stimulation of secondary/transverse flows in the microchannel. The groovebased micromixers generate helical flows within the microchannel to augment the mixing performance. These micromixers are extensively studied with respect to planar geometric parameters such as groove width, groove spacing, channel height, etc. The effect of groove shape on mixing performance has not been systematically studied. Previous studies have focused on two or three different predefined groove shapes, typically involving slanted grooves, asymmetric herringbone grooves, and their variations. In this computational study, we analyze the effect of groove shape on micromixing performance and search for the optimal groove shape for a pressure-driven flow across the microchannel. The groove shape is parametrically represented by Be´zier curves which could take any shape within a constrained plane. The control points of the Be´zier curve are chosen as optimization parameters to identify the optimal groove shape which maximizes the mixing for given operating conditions. The optimization is carried out for pressure-driven flow with and without staggered arrangement of grooves. The resulting single groove optimal design improves the mixing efficiency from 0.18 for T-mixer to 0.85 for the same operating conditions (Re *0.42, Pe *4,200). Unlike previous studies, axial mixing index profiles are presented for different micromixers which clearly distinguish the effect of flow field on the mixing performance. Various parametric studies are carried out to compare the optimal groove structure with other common M. Jain (&) A. Rao K. Nandakumar Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA e-mail: [email protected]
groove type (staggered, herringbone, etc.) micromixers for a range of Pe between 400 and 6,200. The improved mixing performance in optimal designs is due to a continuously growing finger-like structure of the interface which enhances the overall mass transfer. Keywords Micromixing Microfluidics Optimization Groove-mixer
1 Introduction Micromixers are a vital component of biomicrofluidics devices utilized for complex enzyme reactions (Atalay et al. 2009), biochemical analysis (Liu et al. 2008), bio-diagnostics, etc. Microfluidic or Lab-on-a-chip (LOC) devices offer significant benefits over their traditional laboratory counterparts in terms of device size, sample/reagent usage, and analysis time (Whitesides 2006; Chang 2006; Dittrich and Manz 2006). The performance of micromixers directly relates to the analysis time and portability of such devices. The micromixers can be categorized into active and passive mixers (Nguyen and Wu 2005) depending upon their mixing strategy. Active mixers util
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