Numerical Analysis of a Planar O Micromixer with Obstacles


  • Md. Readul Mahmud Department of Physical Sciences, Independent University, Bangladesh (IUB), Dhaka, Bangladesh



Micromixer, Mixing Efficiency, Mixing Cost, CFD


Passive mixers rely on the channel geometry to mix fluids and mixing depends primarily on diffusion.  However, many previously reported designs either work efficiently only at moderate to high Reynolds numbers (Re) or require a complex 3D channel geometry that is often difficult to fabricate. In this paper, we report the design, simulation, and characterization of a planar O passive microfluidic mixer with two types of obstacles to enhance mixing performance. Numerical investigation on mixing and flow structures in microchannels is carried out using the computational fluid dynamics (CFD) software ANSYS 15 for a wide range of Reynolds numbers from 1 to 200. The results show that the O mixer with obstacles has far better mixing performance than the O mixer without obstacles. The reason is that fluid path length becomes longer due to the presence of obstacles which gives fluids more time to diffuse. For all cases, the O mixer with circular & fin obstacles have 3 times more efficient compared to the O mixer without obstacles. It is also clear that efficiency increase with axial length as expected. Efficiency can be simply improved by adding extra mixing units to provide adequate mixing. The value of the pressure drop is the lowest for the O mixer because there is no obstacle inside the channel. However, the O mixer with circular & fin obstacles has the lowest mixing cost, an important characteristic for integration into complex, cascading microfluidic systems, which makes it the most cost-effective mixer. Due to the simple planar structure and low mixing cost, it can be easily realized and integrated into devices for various macromixing applications.


Rahmannezhad, J. and Mirbozorgi, S.A., 2019. CFD analysis and RSM-based design optimization of novel grooved micromixers with obstructions. International Journal of Heat and Mass Transfer, 140, pp.483-497. DOI:

Adeosun, J.T. and Lawal, A., 2009. Numerical and experimental studies of mixing characteristics in a T-junction microchannel using residence-time distribution. Chemical Engineering Science, 64(10), pp.2422-2432. DOI:

Shah, I., Kim, S.W., Kim, K., Doh, Y.H. and Choi, K.H., 2019. Experimental and numerical analysis of Y-shaped split and recombination micro-mixer with different mixing units. Chemical Engineering Journal, 358, pp.691-706. DOI:

Engler, M., Kockmann, N., Kiefer, T. and Woias, P., 2004. Numerical and experimental investigations on liquid mixing in static micromixers. Chemical Engineering Journal, 101(1-3), pp.315-322. DOI:

Schikarski, T., Trzenschiok, H., Peukert, W. and Avila, M., 2019. Inflow boundary conditions determine T-mixer efficiency. Reaction Chemistry & Engineering, 4(3), pp.559-568. DOI:

Shi, X., Huang, S., Wang, L. and Li, F., 2021. Numerical analysis of passive micromixer with novel obstacle design. Journal of Dispersion Science and Technology, 42(3), pp.440-456. DOI:

Mouheb, N.A., Malsch, D., Montillet, A., Solliec, C. and Henkel, T., 2012. Numerical and experimental investigations of mixing in T-shaped and cross-shaped micromixers. Chemical engineering science, 68(1), pp.278-289. DOI:

Hoffmann, M., Schlüter, M. and Räbiger, N., 2006. Experimental investigation of liquid–liquid mixing in T-shaped micro-mixers using μ-LIF and μ-PIV. Chemical engineering science, 61(9), pp.2968-2976.

Dundi, T.M., Raju, V.R.K. and Chandramohan, V.P., 2019. Characterization of mixing in an optimized designed T–T mixer with cylindrical elements. Chinese Journal of Chemical Engineering, 27(10), pp.2337-2351. DOI:

Wong, S.H., Ward, M.C. and Wharton, C.W., 2004. Micro T-mixer as a rapid mixing micromixer. Sensors and Actuators B: Chemical, 100(3), pp.359-379. DOI:

Shamloo, A., Vatankhah, P. and Akbari, A., 2017. Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation. Chemical Engineering and Processing: Process Intensification, 116, pp.9-16. DOI:

Mondal, B., Mehta, S.K., Patowari, P.K. and Pati, S., 2019. Numerical study of mixing in wavy micromixers: comparison between raccoon and serpentine mixer. Chemical Engineering and Processing-Process Intensification, 136, pp.44-61. DOI:

Gidde, R., 2022. On the study of teardrop shaped split and collision (TS-SAC) micromixers with balanced and unbalanced split of subchannels. International Journal of Modelling and Simulation, 42(1), pp.168-177. DOI:

Raza, W., Hossain, S. and Kim, K.Y., 2020. A review of passive micromixers with a comparative analysis. Micromachines, 11(5), p.455. DOI:

Lee, C.Y., Chang, C.L., Wang, Y.N. and Fu, L.M., 2011. Microfluidic mixing: a review. International journal of molecular sciences, 12(5), pp.3263-3287. DOI:

Nguyen, N.T. and Wu, Z., 2005. Micromixers - A review. Journal of Micromechanics and Microengineering, 15(2), pp.1-16. DOI:

Cai, G., Xue, L., Zhang, H. and Lin, J., 2017. A review on micromixers. Micromachines, 8(9), p.274. DOI:

Lee, C.Y., Wang, W.T., Liu, C.C. and Fu, L.M., 2016. Passive mixers in microfluidic systems: A review. Chemical Engineering Journal, 288, pp.146-160. DOI:

Barabash, V.M., Abiev, R.S. and Kulov, N.N., 2018. Theory and practice of mixing: A review. Theoretical Foundations of Chemical Engineering, 52(4), pp.473-487. DOI:

Lee, C.Y. and Fu, L.M., 2018. Recent advances and applications of micromixers. Sensors and Actuators B: Chemical, 259, pp.677-702. DOI:

Bothe, D., Stemich, C. and Warnecke, H.J., 2008. Computation of scales and quality of mixing in a T-shaped microreactor. Computers & Chemical Engineering, 32(1-2), pp.108-114. DOI:

Bothe, D., Lojewski, A. and Warnecke, H.J., 2011. Fully resolved numerical simulation of reactive mixing in a T-shaped micromixer using parabolized species equations. Chemical engineering science, 66(24), pp.6424-6440. DOI:

Galletti, C., Roudgar, M., Brunazzi, E. and Mauri, R., 2012. Effect of inlet conditions on the engulfment pattern in a T-shaped micro-mixer. Chemical Engineering Journal, 185, pp.300-313. DOI:

Tseng, L.Y., Yang, A.S., Lee, C.Y. and Hsieh, C.Y., 2011. CFD-based optimization of a diamond-obstacles inserted micromixer with boundary protrusions. Engineering Applications of Computational Fluid Mechanics, 5(2), pp.210-222. DOI:

Fang, Y., Ye, Y., Shen, R., Zhu, P., Guo, R., Hu, Y. and Wu, L., 2012. Mixing enhancement by simple periodic geometric features in microchannels. Chemical Engineering Journal, 187, pp.306-310. DOI:

Ansari, M.A., Kim, K.Y. and Kim, S.M., 2018. Numerical and experimental study on mixing performances of simple and vortex micro T-mixers. Micromachines, 9(5), p.204. DOI:

Santana, H.S., Silva Jr, J.L., Tortola, D.S. and Taranto, O.P., 2018. Transesterification of sunflower oil in microchannels with circular obstructions. Chinese journal of chemical engineering, 26(4), pp.852-863. DOI:

Lameu da Silva Junior, J., Haddad, V.A., Taranto, O.P. and Silva Santana, H., 2020. Design and analysis of new micromixers based on distillation column trays. Chemical Engineering & Technology, 43(7), pp.1249-1259. DOI:

Tan, S.J., Yu, K.H., Ismail, M.A. and Teoh, Y.H., 2020. Enhanced liquid mixing in T‐mixer having staggered fins. Asia‐Pacific Journal of Chemical Engineering, 15(6), p.e2538. DOI:

Nimafar, M., Viktorov, V. and Martinelli, M., 2012. Experimental investigation of split and recombination micromixer in confront with basic T-and O-type micromixers. Int. J. Mech. Appl, 2(5), pp.61-69. DOI:

Bhagat, A.A.S. and Papautsky, I., 2008. Enhancing particle dispersion in a passive planar micromixer using rectangular obstacles. Journal of micromechanics and microengineering, 18(8), p.085005. DOI:

Mengeaud, V., Josserand, J. and Girault, H.H., 2002. Mixing processes in a zigzag microchannel: finite element simulations and optical study. Analytical chemistry, 74(16), pp.4279-4286. DOI:

Shih, T.R. and Chung, C.K., 2008. A high-efficiency planar micromixer with convection and diffusion mixing over a wide Reynolds number range. Microfluidics and Nanofluidics, 5(2), pp.175-183. DOI:

Bhagat, A.A.S., Peterson, E.T. and Papautsky, I., 2007. A passive planar micromixer with obstructions for mixing at low Reynolds numbers. Journal of micromechanics and microengineering, 17(5), p.1017. DOI:

Shim, J.S., Nikcevic, I., Rust, M.J., Bhagat, A.A.S., Heineman, W.R., Seliskar, C.J., Ahn, C.H. and Papautsky, I., 2007, January. Simple passive micromixer using recombinant multiple flow streams. In Microfluidics, BioMEMS, and Medical Microsystems V (Vol. 6465, pp. 300-307). SPIE. DOI:

Chung, C.K. and Shih, T.R., 2008. Effect of geometry on fluid mixing of the rhombic micromixers. Microfluidics and Nanofluidics, 4(5), pp.419-425. DOI:

Bessoth, F.G., deMello, A.J. and Manz, A., 1999. Microstructure for efficient continuous flow mixing. Analytical communications, 36(6), pp.213-215. DOI:

Lee, S.W., Kim, D.S., Lee, S.S. and Kwon, T.H., 2006. A split and recombination micromixer fabricated in a PDMS three-dimensional structure. Journal of micromechanics and microengineering, 16(5), p.1067. DOI:

Liu, R.H., Stremler, M.A., Sharp, K.V., Olsen, M.G., Santiago, J.G., Adrian, R.J., Aref, H. and Beebe, D.J., 2000. Passive mixing in a three-dimensional serpentine microchannel. Journal of microelectromechanical systems, 9(2), pp.190-197. DOI:

Yuan, S., Zhou, M., Peng, T., Li, Q. and Jiang, F., 2022. An investigation of chaotic mixing behavior in a planar microfluidic mixer. Physics of Fluids, 34(3), p.032007. DOI:

Wong, S.H., Bryant, P., Ward, M. and Wharton, C., 2003. Investigation of mixing in a cross-shaped micromixer with static mixing elements for reaction kinetics studies. Sensors and Actuators B: Chemical, 95(1-3), pp.414-424. DOI:

Stroock, A.D., Dertinger, S.K., Ajdari, A., Mezic, I., Stone, H.A. and Whitesides, G.M., 2002. Chaotic mixer for microchannels. Science, 295(5555), pp.647-651. DOI:

Mariotti, A., Galletti, C., Mauri, R., Salvetti, M.V. and Brunazzi, E., 2018. Steady and unsteady regimes in a T-shaped micro-mixer: Synergic experimental and numerical investigation. Chemical Engineering Journal, 341, pp.414-431. DOI:

Cortes-Quiroz, C.A., Azarbadegan, A. and Zangeneh, M., 2017. Effect of channel aspect ratio of 3-D T-mixer on flow patterns and convective mixing for a wide range of Reynolds number. Sensors and Actuators B: Chemical, 239, pp.1153-1176. DOI:

Orsi, G., Roudgar, M., Brunazzi, E., Galletti, C. and Mauri, R., 2013. Water–ethanol mixing in T-shaped microdevices. Chemical Engineering Science, 95, pp.174-183. DOI:

Viktorov, V., Mahmud, M.R. and Visconte, C., 2016. Design and characterization of a new HC passive micromixer up to Reynolds number 100. Chemical Engineering Research and Design, 108, pp.152-163. DOI:

Tayeb, N.T., Hossain, S., Khan, A.H., Mostefa, T. and Kim, K.Y., 2022. Evaluation of Hydrodynamic and Thermal Behaviour of Non-Newtonian-Nanofluid Mixing in a Chaotic Micromixer. Micromachines, 13(6), p.933. DOI:



  • Abstract view187

How to Cite

Mahmud, M. R. (2022). Numerical Analysis of a Planar O Micromixer with Obstacles. Journal of Engineering Advancements, 3(02), 64–71.



Research Articles