• Title/Summary/Keyword: Chaotic Advection

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Development of an Injection Molded Disposable Chaotic Micromixer: Serpentine Laminating Micromixer (I) - Design and Numerical Analysis - (사출 성형된 일회용 카오스 마이크로 믹서의 개발: 나선형 라미네이션 마이크로 믹서 (I) - 디자인 및 수치 해석 -)

  • Kim Dong Sung;Lee Se Hwan;Kwon Tai Hun;Ahn Chong H.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.10 s.241
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    • pp.1289-1297
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    • 2005
  • The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Serpentine Laminating Micromixer (SLM) in the present study, Part 1. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: splitting/recombination and chaotic advection. The splitting and recombination (in other term, lamination) mechanism is obtained by the successive arrangement of 'F'-shape mixing units in two layers. The chaotic advection is induced by the overall three-dimensional serpentine path of the microchannel. Chaotic mixing performance of the SLM was fully characterized numerically. To compare the mixing performance, a T-type micromixer which has the same width, height and length of the SLM was also designed. The three-dimensional numerical mixing simulations show the superiority of the SLM over the T-type micromixer. From the cross-sectional simulation results of mixing patterns, the chaotic advection effect from the serpentine channel path design acts favorably to realize the ideal lamination of fluid flow as Re increases. Chaotic mixing mechanism, proposed in this study, could be easily integrated in Micro-Total-Analysis-System, Lab-on-a-Chip and so on.

Development of an Injection Molded Disposable Chaotic Micromixer: Serpentine Laminating Micromixer (II) - Fabrication and Mixing Experiment - (사출 성형된 일회용 카오스 마이크로 믹서의 개발: 나선형 라미네이션 마이크로 믹서 (II) - 제작 및 혼합 실험 -)

  • Kim Dong Sung;Lee Se Hwan;Kwon Tai Hun;Ahn Chong H.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.10 s.241
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    • pp.1298-1306
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    • 2005
  • In this paper, Part II, we realized the Serpentine Laminating Micromirer (SLM) which was proposed in the accompanying paper, Part I, by means of the injection molding process in mass production. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms of splitting/recombination and chaotic advection by the successive arrangement of 'F'-shape mixing units in two layers. Mold inserts for the injection molding process of the SLM were fabricated by SU-8 photolithography and nickel electroplating. The SLM was realized by injection molding of COC (cyclic olefin copolymer) with the fabricated mold inserts and thermal bonding of two injection molded COC substrates. To compare the mixing performance, a T-type micromixer was also fabricated. Mixing performances of micromixers were experimentally characterized in terms of an average mixing color intensity of a pH indicator, phenolphthalein. Experimental results show that the SLM has much better mixing performance than the I-type micromixer and chaotic mixing was successfully achieved from the SLM over the wide range of Reynolds number (Re). The chaotic micromixer, SLM proposed in this study, could be easily integrated in Micro-Total-Analysis- System , Lab-on-a-Chip and so on.

The study of three dimentional flow field using defocusing method in micromixer (Defocusing 기법을 이용한 마이크로 믹서내의 3 차원 유동장 측정연구)

  • Kim, Su-Heon;Yoon, Sang-Youl;Kim, Kyung-Chun
    • 한국가시화정보학회:학술대회논문집
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    • 2005.12a
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    • pp.99-102
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    • 2005
  • This study was conducted for obtaining the optimized data to build the mixer or micro fluid device as measuring the three dimensions flow field in micro mixer. To acquire the rapid diffusion on the region of low Reynolds (Re < 100), the staggered herringbone mixer using chaotic advection was selected in this case. At first, by conducting the numerical analytical virtual experiment using CFD-ACE+, three dimensions flow field in the micro mixer was estimated As this flow field was proven using defocusing particle tracing method, the behavior of micro flow with three dimensional aspects could be analyzed. Numerical analysis and flow pattern in the micro mixer by experimental verification made to be able to analyze the chaotic advection. These can be important sources for building more optimized form. Verifying the information of three dimensional flow structure, these information can be used as the data for developing and improving the $\mu$ -TAS.

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Prediction of Degree of Mixing for Insoluble Solution with Vortex Index in a Passive Micromixer (마이크로 믹서에서 와도 지수에 의한 비용해성 물질의 혼합 예측)

  • Cho Il-dae;Kim Bum-joong;Maeng Joo-sung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.2 s.233
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    • pp.232-238
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    • 2005
  • The 'Mixing Index($D_I$)' is used as a conventional guidance measuring the degree of mixing for multiphase flows. For the case when insoluble solutions flow in a passive micromixer, a new method to calculate $D_I$ is proposed. The 'Vortex Index(${\Omega}_I$)' is suggested and formulated. We infer that ${\Omega}_I$ relates to the degree of chaotic advection. Various arbitrary shaped microchannels were tested to calculate the $D_I\;and\;{\Omega}_I$, and then a simple algebraic equation, $D_I=Aexp(B{\Omega}_I)$, is obtained. This equation may be used instead of the conventional partial differential equation, concentration equation, to estimate the degree of mixing.

Method of Material-Stretching Mapping for Quantification of Mixing Effect in Microchannels (마이크로 채널 내의 혼합효과 정량화를 위한 물질신장 사상법)

  • Suh Y. K.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.04a
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    • pp.1-13
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    • 2005
  • Fluid flows within microchannels are characterized by low Reynolds numbers. Therefore the effect of mixing is a crucial factor in design of the channels. Since the action of the electro-osmotic or magnetic forces used in the mixing enhancement is usually periodic in the three-dimensional channel configuration, use of the various concepts of chaotic advection is reasonable in the quantification of the stirring effect. In this paper, the details of the method of material-stretching mapping is explained. The actual application of the method to the screw extruder is also presented.

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The Relation between Vortex Index and Mixing Index in Micromixer;Insoluble Solution;Insoluble Solution (마이크로 믹서에서 와도 지수와 혼합 지수의 관계;비용해성 물질)

  • Maeng, Joo-Sung;Kim, Bum-Joong;Cho, Il-dae
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1841-1844
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    • 2004
  • 'Mixing Index($D_I$)'s generally used to measure the degree of mixing. A new method to calculate $D_I$ was proposed, when insoluble solution flows in micromixer. 'Vortex Index (${\Omega}_I$)'which indicate the degree of chaotic advection, is defined and formulated. A lots of arbitrary shaped microchannels were tested to calculate the $D_I$ and ${\Omega}_I$. And then a simple algebraic equation, $D_I=A{\Omega}_I+B$, was obtained. This equation may be used instead of partial differential equation, concentration equation.

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Numerical Study for Mixing Characteristics of an Oscillating Micro-stirrer (미소진동교반기의 혼합특성에 대한 수치적 연구)

  • Kim, Yong-Dae;Maeng, Joo-Sung
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.309-312
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    • 2006
  • Effective mixing is an important problem in microfluidics for chemical and biomechanical applications. In this study, the influences of the Reynolds number and the oscillating frequency on mixing characteristics of micro-stirrer are studied in a microchannel with single stirrer. The influence of fluid inertial effects in an active mixer is first discussed. It is found that the stirring effects by stirrer oscillation are promptly attenuated at low Reynolds number, which makes greatly difficult the rapid mixing. As the inertial effects are increased, the chaotic advection is generated and then developed. The mixing phase is finally developed some mushroom shaped structure. And the mixing efficiency is also studied as a function of the oscillating frequency. We found that the mixing efficiency does not always increase with higher oscillating frequency of stirrer. Consequently, we found the functional relation between the optimal frequency of a stirrer and the Reynolds number.

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A NUMERICAL STUDY ON FLOW AND STIRRING CHARACTERISTICS IN A MICROCHANNEL WITH PERIODIC ARRAY OF CROSS BAFFLES (엇갈림 배플 구조의 마이크로 채널 내 유동 및 혼합 특성에 관한 수치해석적 연구)

  • Heo, S.G.;Kang, S.M.;Suh, Y.K.
    • Journal of computational fluids engineering
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    • v.11 no.4 s.35
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    • pp.101-106
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    • 2006
  • In the microfluidic devices the most important thing is mixing efficiency ol various fluids. In this study a newly designed miler is proposed to enhance the mixing effect with the purpose to apply it to microchannel mixing in a short future. This design is composed of a channel with cross baffles periodically arranged on the both bottom and top surfaces ol the channel. To obtain the yow patterns, the numerical computation was performed by using a commercial code, ANSYS CFX 10.0. To evaluate the mixing performance, we computed Lyapunov exponent and obtained Poincare sections. it was shown that our design provides the excellent mixing effect.

A NUMERICAL STUDY ON FLOW AND STIRRING CHARACTERISTICS IN A MICROCHANNEL WITH PERIODIC ARRAY OF CROSS BAFFLES (엇갈림 배플 구조의 마이크로 채널 내 유동 및 혼합 특성에 관한 수치해석적 연구)

  • Heo, S.G.;Heo, Y.G.;Heo, H.S.;Suh, Y.K.
    • 한국전산유체공학회:학술대회논문집
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    • 2006.10a
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    • pp.159-162
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    • 2006
  • In the microfluidics devices the most important thing is mixing efficiency of various fluids. In this study a newly designed mixer is proposed to enhance the mixing effect with the purpose to apply it to microchannel mixing in a short future. This design is composed of a channel with cross baffles periodically arranged on the both bottom and top surfaces of the channel. To obtain the flow patterns, the numerical computation was performed by using a commercial code, ANSYS CFX 10.0. To evaluate the mixing performance, we computed Lyapunov exponent and obtained Poincare sections.

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On the Problem of Using Mixing Index Based on the Concentration Dispersion (농도분산에 근거한 혼합지수 사용의 문제)

  • Suh Yong-Kweon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.8 s.251
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    • pp.796-805
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    • 2006
  • In this study, the problem of using the mixing index as a measure of the mixing performance for a certain flow field has been discussed. The flow model subjected to this study is the two-dimensional unsteady lid-driven cavity flow. The transport equation for the concentration within the cavity was solved by using the finite volume method where the convective terms are discretized with the central difference scheme. It was shown that both the concentration dispersion and the mixing index depend highly on the initial distribution of the concentration, and therefore the mixing index obtained from the concentration dispersion equation loses its universal applicability.