Enhancement of mixing within a micro cavity by use of transient induced-charge electro-osmotic flow around micro electrodes

Alapati, Suresh,Fernandes, Dolfred Vijay,Suh, Yong-Kweon 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.6

This paper presents a numerical study on the enhancement of mixing within a micro cavity by use of transient induced-charge electro-osmotic flows created by a periodic on-off-switching of the electric field applied across a pair of electrodes. For the first time, we demonstrate that the electro-osmotic flows observed during the charging and decharging stages are not symmetric with respect to each other and can lead to a chaotic mixing. Lyapunov exponents and particle scattering patterns are obtained for the symptom of the chaotic advection at various external fields.

정적 혼합기에서 요변성 유체의 유동 및 혼합 특성에 관한 수치해석

박조은(Jo-Eun Park),강태곤(Tae Gon Kang),문희장(Hee Jang Moon),정선엽(Seon Yeop Jung),박준동(Jun Dong Park) 한국추진공학회 2020 한국추진공학회 학술대회논문집 Vol.2020 No.11

정적 혼합기(Static Mixer)에서 요변성 유체(Thixotropic Fluid)의 유동과 혼합 특성에 대한 수치해석을 수행하였다. 이 연구의 주된 관심사는 요변성 유체의 유변학적 특성이 유동과 혼합에 미치는 영향이다. 요변성 유체의 구조인자를 모사하기 위해 Moore 모델을 채택하였고 요변성 유체의 구조-운동 방정식을 질량보존, 운동량보존식과 결합하여 유한체적법을 이용하여 계산하였다. 본 연구에서는 카오스 혼합을 발생시키기 위해 정적 혼합기를 도입하였다. 요변성 유체의 구조인자 분포와 푸앵카레 단면(Poincaré section)을 이용하여 요변성 유체의 유동 및 혼합 특성을 확인하였다. We conducted numerical simulations on the flow and mixing characteristics of a thixotropic fluid in a static mixer. Our main focus is on the effect of dimensionless parameters on the chaotic mixing of the thixotropic fluid. A Moore model is applied to represent the evolution of structure parameter for the thixotropic fluid. Finite volume method is employed to solve the structure-kinetics equation coupled with the steady Navier-Stokes equation. A groove-embedded partitioned pipe mixer (GPPM), a static mixer based on chaotic advection, is introduced to investigate mixing. Distributions of the structure factor and Poincaré sections are plotted to characterize the flow and mixing affected by the dimensionless number ĸ in laminar flow regime.

논 엘레멘트 믹서의 혼합 메커니즘에 관한 수치해석적 검토

유선호 ( Sun Ho You ) 한국분무공학회 2015 한국액체미립화학회지 Vol.20 No.1

Visualization of the mixing pattern in a non-element mixer was carried out using laser induced fluorescence(LIF) to eval- uate characteristics of mixer consisting of the main flow pipe and branch flow pipes. The branch flows were injected peri- odically with the period Tin normal to the main flow, and rhodamine B was mixed into the most upstream branch flow to visualize mixing pattern in the main flow pipe by LIF. The length of boundary line L of the LIF image was measured. In this study, a numerical analysis was performed to identify the mixing process of the non-element mixer, and the results were compared with experimental results. Each result was almost the same. When the number of branch flows is increased, the mixing pattern became complicated and was supposed to become chaotic. The length of boundary line L increased exponen- tially with an increase in the number of branch flows.

마이크로 믹서에서 와도 지수와 혼합 지수의 관계(비용해성 물질)

맹주성(Joo-sung Maeng),김범중(Bum-joong Kim),조일대(Il-dae Cho) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

“Mixing Index(D<SUB>I</SUB>)” is generally used to measure the degree of mixing. A new method to calculate D<SUB>I</SUB> was proposed, when insoluble solution flows in micromixer. “Vortex Index (Ω<SUB>I</SUB>)” which indicate the degree of chaotic advection, is defined and formulated. A lots of arbitrary shaped microchannels were tested to calculate the D<SUB>I</SUB> and Ω<SUB>I</SUB>. And then a simple algebraic equation, D<SUB>I</SUB> = AΩ<SUB>I</SUB>+B, was obtained. This equation may be used instead of partial differential equation, concentration equation.

CHAOTIC MIXING IN SQUARE CAVITY FLOW

T.H.V Le(레뛰홍반),S. Kang(강상모),Y.K. Suh(서용권) 한국전산유체공학회 2007 한국전산유체공학회 학술대회논문집 Vol.2007 No.-

The quality of chaotic mIXing in square cavity flow was studied numerically by CFD simulation and particle tracking technique. The chaotic mixing was generated by using time-periodic electro-osmotic flow. Finite Volume Method (FVM) was employed to get the stretching and folding field in cavity domain. With adjusting the initial condition of concentration distribution, the best values of modulation period and Peclet number which gave us good mixing performance was determined precisely. From Poicaresection and Lyapunov exponents for characteristic trajectories we find that mixing performance also depends on modulation period. The higher value of modulation period, the better mixing performance was achieved in this case. Furthermore, the results for tracking particle trajectories were also compared between using of Bilinear Interpolation and Higher-order scheme. The values of modulation period for obtaining best mixing effect were matched between using FVM and particle tracking techniques.

Chaotic Mixing in Two-Dimensional Square Cavity Flow by Using Finite Volume Method (FVM)

Thuy Hong Van- Le,Sang Mo Kang,Yong Kweon Suh 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

Chaotic mixing inside two-dimensional square cavity was examined numerically. Finite volume method, known as one of the most efficient numerical methods recently, is employed to obtain accurate descriptions of the velocities fields which form the basis of mixing analysis. The primary form of chaotic mixing of this case is caused by imposing a non-uniform boundary conditions which periodically apply to bottom wall at a first half of the period and to the top wall at a second half of the period, respectively. There are several parameters in this flow model; these are the Peclet number and modulation period. We will investigate numerically how these parameters affect the flow patterns within the cavity. There is also an important value, mixing index which descript the quality of mixing is obtained in this case. The numerical results to be obtained in this study can be used as bench-mark solutions in developing FVM codes.

Chaotic Mixing in Two-Dimensional Square Cavity Flow Using Finite Volume Method (FVM)

Thuy Hong Van-Le,Yong Kweon Suh,Sang Mo Kang 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

Chaotic mixing inside two-dimensional square cavity was examined numerically. Finite volume method is employed to obtain accurate descriptions of the velocities field which form the basis of mixing analysis. The primary form of chaotic mixing of this case is caused by imposing the non-uniform boundary conditions which is periodically applied to bottom wall at a first half of the period and to the top wall at a second half of the period, respectively. There are several parameters in this flow model; these are the Peclet number and modulation period. We will investigate numerically how these parameters affect the flow patterns within the cavity. There is also an important value, mixing index which descript the quality of mixing is obtained in this case. Furthermore, we will get the mixing efficiency using Poincare section and Lyapunov exponent. The numerical results to be obtained in this study can be used as bench-mark solutions in developing FVM codes.

Numerical study on the mixing in a barrier-embedded partitioned pipe mixer (BPPM) for non-creeping flow conditions

정해인,정선엽,강태곤,안경현 한국유변학회 2018 Korea-Australia rheology journal Vol.30 No.3

In this paper we investigated numerically the flow and mixing characteristics of the barrier-embedded partitioned pipe mixer (BPPM) in non-creeping flow conditions. Numerical simulations are conducted for three mixing protocols of the BPPM, co-rotational, mirrored co-rotational, and counter-rotational protocols in the range of the Reynolds number (Re), , focusing on the effect of the Reynolds number, the barrier height, and the mixing protocols on the mixing in the BPPM. Each mixing protocol creates two crosssectional flow portraits with crossing streamlines. Poincaré sections were plotted to investigate the flow system affected by the Reynolds number and the barrier height. Mixing in a specific BPPM is characterized using the intensity of segregation in terms of the compactness and the energy consumption. The dependency of the barrier height and the Reynolds number on the final mixing state of the BPPMs was identified by mixing analyses. The co-rotational protocol results in an efficient mixing in the creeping flow regime. Meanwhile, mirrored co-rotational and counter-rotational protocols, which lead to poor mixing in the creeping flow regime, turned out to be efficient protocols in the higher Reynolds number regime.

Experimental investigation of mixing in a novel continuous chaotic mixer

Seyyed Mostafa Hosseinalipour,Amir Tohidi,Payam Rahim Mashaei,Arun Sadashiv Mujumdar 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.10

This paper presents and discusses results of an experimental study of laminar mixing of a highly viscousfluid (dough) in a continuous chaotic mixer. The mixer consists of an eccentric rotor that rotates co-axially within astator, which results in chaotic advection. A dye injection technique was used to measure the mixing performance ofthe mixer. A mixing index was defined and computed by image processing of photographs of the exiting fluid fromthe mixer. Mixing characteristics were determined for constant as well as stepwise rotation of the rotor. Results revealedthat mixing performance improves with increase in the rotational speed for constant rotational speed. The stepwiserotation case displayed better mixing performance than the constant speed case for stepwise changes of the amplitude aswell as frequency of rotation.

Global measures of distributive mixing and their behavior in chaotic flows

Tucker, Charles L.,Peters, Gerrit W.M. The Korean Society of Rheology 2003 Korea-Australia rheology journal Vol.15 No.4

Two measures of distributive mixing are examined: the standard deviation $\sigma$ and the maximum error E, among average concentrations of finite-sized samples. Curves of E versus sample size L are easily interpreted in terms of the size and intensity of the worst flaw in the mixture. E(L) is sensitive to the size of this flaw, regardless of the overall size of the mixture. The measures are used to study distributive mixing for time-periodic flows in a rectangular cavity, using the mapping method. Globally chaotic flows display a well-defined asymptotic behavior: E and $\sigma$ decrease exponentially with time, and the curves of E(L) and $\sigma$ (L) achieve a self-similar shape. This behavior is independent of the initial configuration of the fluids. Flows with large islands do not show self-similarity, and the final mixing result is strongly dependent on the initial fluid configuration.