Numerical investigation of mixing performance in spiral micromixers based on Dean flows and chaotic advection

Micromixer is essential component of microfluidic system which has wide application in the field of chemistry and biochemistry. A highly efficient and easily fabricated three dimensional micromixer based on chaotic advection is proposed and investigated. The depth of 25μm for each layer of micromixer and two kinds of fluids, which have viscosities of 0.00097kgm-1s-1and 0.186kgm-1s-1with Re number from 0.001 to 150, are adopted for numerical investigation of mixing efficiency by using ANSYS-Fluent. High mixing index of more than 90% can be obtained by using less than 300μm of length under Re number of 0.01 for mixing Fluid 1. However, it requires 850μm to achieve mixing index of more than 90% for hard-to-mix Fluid 2.

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Improved Serpentine Laminating Micromixer: Numerical Investigation and Experimental Verification

ASME 5th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2007-30204 ◽

2007 ◽

Author(s):

Jang Min Park ◽

Dong Sung Kim ◽

Tae Gon Kang ◽

Tai Hun Kwon

Keyword(s):

Numerical Analysis ◽

Experimental Verification ◽

Flow Characteristics ◽

Chaotic Advection ◽

Intensity Change ◽

Chaotic Mixing ◽

Cross Sectional ◽

Mixing Performance ◽

Optical Micrograph ◽

Particle Tracking Method

It is a difficult task to achieve an efficient mixing inside a microchannel since the flow is characterized by low Reynolds number (Re). Recently, the serpentine laminating micromixer (SLM) was reported to achieve an efficient chaotic mixing by introducing ‘F’-shape mixing units successively in two layers such that two chaotic mixing mechanisms, namely splitting/recombination and chaotic advection, enhance the mixing performance in combination. The present study describes an improved serpentine laminating micromixer (ISLM) with a novel redesign of the ‘F’-shape mixing unit. Reduced cross-sectional area at the recombination region of ISLM locally enhances advection effect which helps better vertical lamination, resulting in improved mixing performance. Flow characteristics and mixing performances of SLM and ISLM are investigated numerically and verified experimentally. Numerical analysis system is developed based on a finite element method and a colored particle tracking method, while mixing entropy is adopted as a quantitative mixing measure. Numerical analysis result confirms enhanced vertical lamination performance and consequently improved mixing performance of ISLM. For experimental verification, SLM and ISLM were fabricated by polydimethylsiloxane (PDMS) casting against SU-8 patterned masters. Mixing performance is observed by normalized red color intensity change of phenolphthalein along the downchannel. Flow characteristics of SLM and ISLM are investigated by tracing the red interface of two streams via optical micrograph. The normalized mixing intensity behavior confirms improved mixing performance of ISLM, which is consistent with numerical analysis result.

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Numerical investigation of chaotic advection past a groyne based on laboratory flow experiment

Advances in Water Resources ◽

10.1016/j.advwatres.2014.06.004 ◽

2014 ◽

Vol 71 ◽

pp. 81-92 ◽

Cited By ~ 7

Author(s):

Márton Zsugyel ◽

Tamás Tél ◽

János Józsa

Keyword(s):

Numerical Investigation ◽

Chaotic Advection ◽

Flow Experiment

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Numerical Investigation of Liquid–Liquid Mixing in Modified T Mixer with 3D Obstacles

Journal of Engineering Advancements ◽

10.38032/jea.2021.02.004 ◽

2021 ◽

pp. 25-32

Author(s):

Md. Readul Mahmud

Keyword(s):

Numerical Investigation ◽

Stokes Equations ◽

Three Dimensional ◽

Flow Characteristics ◽

Reynolds Numbers ◽

Channel Length ◽

Navier Stokes ◽

Mixing Efficiency ◽

Mixing Performance ◽

Wide Range

The fluids inside passive micromixers are laminar in nature and mixing depends primarily on diffusion. Hence mixing efficiency is generally low, and requires a long channel length and longtime compare to active mixers. Various designs of complex channel structures with/without obstacles and three-dimensional geometries have been investigated in the past to obtain an efficient mixing in passive mixers. This work presents a design of a modified T mixer. To enhance the mixing performance, circular and hexagonal obstacles are introduced inside the modified T mixer. Numerical investigation on mixing and flow characteristics in microchannels is carried out using the computational fluid dynamics (CFD) software ANSYS 15. Mixing in the channels has been analyzed by using Navier–Stokes equations with water-water for a wide range of the Reynolds numbers from 1 to 500. The results show that the modified T mixer with circular obstacles has far better mixing performance than the modified T mixer without obstacles. The reason is that fluids' path length becomes longer due to the presence of obstacles which gives fluids more time to diffuse. For all cases, the modified T mixer with circular obstacle yields the best mixing efficiency (more than 60%) at all examined Reynolds numbers. It is also clear that efficiency increase with axial length. 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 modified T mixer because there is no obstacle inside the channel. Modified T mixer and modified T mixer with circular obstacle have the lowest and highest mixing cost, respectively. Therefore, the current design of modified T with circular obstacles can act as an effective and simple passive mixing device for various micromixing applications.

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Numerical Investigation on Multiphase Flows in Various Configurations of Microchannels Using Computational Fluid Dynamics

ASEAN Journal of Chemical Engineering ◽

10.22146/ajche.49568 ◽

2019 ◽

Vol 17 (1) ◽

pp. 82

Author(s):

Mohd Fadhil Majnis ◽

Mohamad Rawad Jalwan

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Fluid Flows ◽

Chaotic Advection ◽

Computational Domain ◽

Mixing Performance ◽

Vof Model ◽

Computational Fluid Dynamics Cfd ◽

Miscible Liquids ◽

Grid Independence

A two-dimensional domain of multiphase flow analyses in this study using the Volume of Fluid (VOF) model was carried out in order to simulate and predict the fluid flows and mixing performance of two miscible liquids in various microchannel configurations. The various microchannels configurations were designed accordingly and the simulation was carried out based on the justified conditions, assumptions and considerations by using the commercial computational fluid dynamics (CFD) software, FLUENT. The grid type and size of the computational domain were verified in terms of stability by performing the grid independence analysis. The result showed that static mixing would be possible to achieve in various configurations of microchannels, however, the simulation results predicted that it appeared to be more efficient in complex and retrofitted microchannels. It showed the potential to promote and enhance chaotic advection, compositions distribution, and diffusivity as compared to basic microchannels that are mostly dependent only on the injection focus. Furthermore, the Reynolds number appeared to be a significant factor to enhance the mixing performance in microchannel beside the configurations.

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Numerical Analysis of Liquid Mixing in a T-Micromixer with Taylor Dispersion Obstructions

International Journal of Mathematical Engineering and Management Sciences ◽

10.33889/ijmems.2020.5.1.013 ◽

2019 ◽

Vol 5 (1) ◽

pp. 147-160

Author(s):

T. Manoj Dundi ◽

S. Chandrasekhar ◽

Shasidar Rampalli ◽

V. R. K. Raju ◽

V. P. Chandramohan

Keyword(s):

Biomedical Engineering ◽

Flow Direction ◽

Taylor Dispersion ◽

Chaotic Advection ◽

Mixing Enhancement ◽

Chemical Processing ◽

Inertial Effects ◽

Mixing Performance ◽

Velocity Gradients

Passive micromixers are of great importance in biomedical engineering (lab-on-chips) and chemical processing (microreactors) fields. Various hydrodynamic principles such as lamination, flow separation, and chaotic advection were employed previously to improve mixing in passive mixers. However, mixing enhancement due to velocity gradients in the flow, which is known as the Taylor dispersion effect, has been seldom studied. In the present study, thin rectangular slabs oriented in the flow direction are placed in the mixing channel of a T-micromixer. The thin rectangular slabs are referred to as Taylor Dispersion Obstructions (TDOs) as they are designed to create velocity gradients in the flow. The mixing performance of T-micromixer with and without TDOs is estimated in the Re range of 0 to 350. It is observed that there is no effect on mixing in the presence of TDOs in the low Re (0 < Re < 100), as the velocity gradients created in the flow are considerably small. The vortex formed in the flow for Re of 100 to 220 damped the gradients of velocity created in the flow (due to the presence of TDOs) which resulted in negligible improvement in the quality of mixing. However, considerable enhancement in mixing performance is obtained at high Re (250 to 350) with the presence of TDOs in the mixer. The increase in inertial effects at higher Recreated larger gradients of velocity near the walls of TDOs and mixing channel walls and thereby a significant enhancement in mixing performance is obtained due to Taylor dispersion.

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