Novel micromixers driven by flow instabilities: Application to post‐reactors

Flow-driven instabilites in microdevices, consisting of small features (posts), are studied using 2-D computational fluid dynamics simulations as a means of enhanching mixing at the microscale. It is found that oscillatory flow developed above a critical Reynolds number in the wake of a post is weakly affected by volumetric and surface (catalytic) reactions. The observed reactivity, on the other hand, is strongly affected by flow-driven instabilities. Based on these results, a novel post micromixer that capitalizes on this oscillatory flow while exhibiting a low pressure drop is proposed. Finally, different feature configurations are investigated to gain insights into the mixing performance and to develop design guidelines. © 2005 American Institute of Chemical Engineers AIChE J, 2005

[1]  I. Mezić,et al.  Chaotic Mixer for Microchannels , 2002, Science.

[2]  Mitutosi Kawaguti,et al.  Numerical Study of a Viscous Fluid Flow past a Circular Cylinder , 1966 .

[3]  K. Jensen,et al.  Design and fabrication of microfluidic devices for multiphase mixing and reaction , 2002 .

[4]  Christopher J. Freitas,et al.  Perspective: Selected Benchmarks From Commercial CFD Codes , 1995 .

[5]  M. M. Zdravkovich,et al.  REVIEW—Review of Flow Interference Between Two Circular Cylinders in Various Arrangements , 1977 .

[6]  Morteza Gharib,et al.  Ordered and chaotic vortex streets behind circular cylinders at low Reynolds numbers , 1987, Journal of Fluid Mechanics.

[7]  Uwe Fey,et al.  A new Strouhal–Reynolds-number relationship for the circular cylinder in the range 47 , 1998 .

[8]  A. Roshko.  On the development of turbulent wakes from vortex streets , 1953 .

[9]  Saif A. Khan,et al.  Transport and reaction in microscale segmented gas-liquid flow. , 2004, Lab on a chip.

[10]  Dionisios G. Vlachos,et al.  From Density Functional Theory to Microchemical Device Homogenization: Model Prediction of Hydrogen Production For Portable Fuel Cells , 2004 .

[11]  D. Guillaume,et al.  Investigation of the flopping regime with two-, three- and four-cylinder arrays , 1999 .

[12]  C. P. Jackson.  A finite-element study of the onset of vortex shedding in flow past variously shaped bodies , 1987, Journal of Fluid Mechanics.

[13]  C. Mavridis,et al.  Isothermal and non-premixed turbulent reacting wake flows past a two-dimensional square cylinder , 1998 .

[14]  J. Khinast,et al.  Reactive mass transfer at gas–liquid interfaces: impact of micro-scale fluid dynamics on yield and selectivity of liquid-phase cyclohexane oxidation , 2003 .

[15]  Dionisios G. Vlachos,et al.  Microreactor Modeling for Hydrogen Production from Ammonia Decomposition on Ruthenium , 2004 .

[16]  Chun-Ping Jen,et al.  Design and simulation of the micromixer with chaotic advection in twisted microchannels. , 2003, Lab on a chip.

[17]  Bernie D. Shizgal,et al.  A Chebyshev pseudospectral multi-domain method for steady flow past a cylinder up to Re = 150 , 1994 .

[18]  Edmund G Seebauer,et al.  Porous anodic alumina microreactors for production of hydrogen from ammonia , 2004 .

[19]  Wolfgang Ehrfeld,et al.  Characterization of Mixing in Micromixers by a Test Reaction: Single Mixing Units and Mixer Arrays , 1999 .

[20]  K. Jensen.  Microreaction engineering * is small better? , 2001 .

[21]  P. Tabeling,et al.  Chaotic mixing in cross-channel micromixers , 2004, Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[22]  Kurt A. Kraus,et al.  Interaction of Vortex Streets , 1964 .

[23]  Chih-Yung Wen,et al.  Two-dimensional vortex shedding of a circular cylinder , 2001 .

[24]  R. Chhabra,et al.  Wall effects in flow past a circular cylinder in a plane channel: a numerical study , 2004 .

[25]  Hassan Aref,et al.  Designing for chaos: applications of chaotic advection at the microscale , 2004, Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[26]  Sanjay Mittal,et al.  Unsteady incompressible flows past two cylinders in tandem and staggered arrangements , 1997 .

[27]  S. Mittal,et al.  Incompressible flow past a circular cylinder: dependence of the computed flow field on the location of the lateral boundaries , 1995 .

[28]  G. Whitesides,et al.  Microfabrication inside capillaries using multiphase laminar flow patterning , 1999, Science.

[29]  V Hessel,et al.  An optimised split-and-recombine micro-mixer with uniform chaotic mixing. , 2004, Lab on a chip.

[30]  M. Braza,et al.  Numerical study and physical analysis of the pressure and velocity fields in the near wake of a circular cylinder , 1986, Journal of Fluid Mechanics.

[31]  M. Kiya,et al.  Vortex Shedding From Two Circular Cylinders in Staggered Arrangement , 1980 .

[32]  Steffen Hardt,et al.  Simulation of helical flows in microchannels , 2004 .

[33]  Haecheon Choi,et al.  Numerical solutions of flow past a circular cylinder at Reynolds numbers up to 160 , 1998 .

[34]  Bartosz A Grzybowski,et al.  Microfluidic mixers: from microfabricated to self-assembling devices , 2004, Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[35]  T. Johnson,et al.  Rapid microfluidic mixing. , 2002, Analytical chemistry.

[36]  K. Lam,et al.  Force coefficients and Strouhal numbers of four cylinders in cross flow , 2003 .

[37]  David F. Fletcher,et al.  Simulation of the Flow around Spacer Filaments between Channel Walls. 2. Mass-Transfer Enhancement , 2002 .

[38]  M. Fichtner,et al.  Microstructured Rhodium Catalysts for the Partial Oxidation of Methane to Syngas under Pressure , 2001 .

[39]  D. Young,et al.  Simulation of laminar vortex shedding flow past cylinders using a coupled BEM and FEM model , 2001 .

[40]  Steffen Hardt,et al.  Laminar mixing in different interdigital micromixers: II. Numerical simulations , 2003 .

[41]  Robin H. Liu,et al.  Passive mixing in a three-dimensional serpentine microchannel , 2000, Journal of Microelectromechanical Systems.

[42]  J. Li,et al.  Numerical study of Laminar flow past one and two circular cylinders , 1991 .

[43]  Hasan Karim,et al.  Complete and partial catalytic oxidation of methane over substrates with enhanced transport properties , 2003 .

[44]  J. Gerrard.  The wakes of cylindrical bluff bodies at low Reynolds number , 1978, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[45]  Carl A. Friehe,et al.  Vortex shedding from cylinders at low Reynolds numbers , 1980, Journal of Fluid Mechanics.

[46]  Wolfgang Ehrfeld.  Design guidelines and manufacturing methods for microreaction devices , 2002 .

[47]  Hiroshi Goto,et al.  Ultrasonic micromixer for microfluidic systems , 2000, Proceedings IEEE Thirteenth Annual International Conference on Micro Electro Mechanical Systems (Cat. No.00CH36308).

[48]  Kwang-Seok Yun,et al.  Microfluidic components and bio-reactors for miniaturized bio-chip applications , 2004 .

[49]  A. T. Sayers,et al.  Vortex shedding from groups of three and four equispaced cylinders situated in a cross flow , 1990 .

[50]  Robert L. Lee,et al.  A MODIFIED FINITE ELEMENT METHOD FOR SOLVING THE TIME-DEPENDENT, INCOMPRESSIBLE NAVIER-STOKES EQUATIONS. PART 1: THEORY* , 1984 .

[51]  Klaus Drese,et al.  Optimization of interdigital micromixers via analytical modeling—exemplified with the SuperFocus mixer , 2004 .

[52]  Dionisios G. Vlachos,et al.  Fabrication of Single-Channel Catalytic Microburners: Effect of Confinement on the Oxidation of Hydrogen/Air Mixtures , 2004 .

[53]  M. Provansal,et al.  Bénard-von Kármán instability: transient and forced regimes , 1987, Journal of Fluid Mechanics.

[54]  M. Provansal,et al.  The Benard-Von Karman instability : an experimental study near the threshold , 1984 .

[55]  Thomas Schwalbe,et al.  Chemical synthesis in microreactors , 2002 .

[56]  K. Lam,et al.  Phenomena of vortex shedding and flow interference of three cylinders in different equilateral arrangements , 1988, Journal of Fluid Mechanics.

[57]  R. Bouard,et al.  Experimental determination of the main features of the viscous flow in the wake of a circular cylinder in uniform translation. Part 1. Steady flow , 1977, Journal of Fluid Mechanics.

[58]  Sang-Hyo Kim,et al.  Microfluidic device for bio analytical systems , 2004 .

[59]  M. D. Croon,et al.  Miniaturization of heterogeneous catalytic reactors : prospects for new developments in catalysis and process engineering , 2002 .

[60]  A. Johnson,et al.  Numerical simulation of flows past periodic arrays of cylinders , 1993 .

[61]  M. M. Zdravkovich,et al.  Flow induced oscillations of two interfering circular cylinders , 1985 .

[62]  W. Price,et al.  A CELL BOUNDARY ELEMENT METHOD APPLIED TO LAMINAR VORTEX-SHEDDING FROM ARRAYS OF CYLINDERS IN VARIOUS ARRANGEMENTS , 2000 .

[63]  B. R. Noack,et al.  On chaos in wakes , 1992 .

[64]  R. Henderson,et al.  Three-dimensional Floquet stability analysis of the wake of a circular cylinder , 1996, Journal of Fluid Mechanics.

[65]  E. Berger,et al.  Periodic Flow Phenomena , 1972 .

[66]  T. Griffin,et al.  Micro-engineered catalyst systems: ABB’s advancement in structured catalytic packings , 2001 .

[67]  C. Williamson.  Vortex Dynamics in the Cylinder Wake , 1996 .

[68]  R. Grundmann,et al.  Numerical Simulation of the Flow Around an Infinitely Long Circular Cylinder in the Transition Regime , 2001 .