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Behavior of Oil-Water Interface between Tandem Fences
강관형,이정묵,Kang Kwan Hyoung,Lee Choung Mook 한국해양환경·에너지학회 1999 한국해양환경·에너지학회지 Vol.2 No.2
와류에 의한 이중 유벽 사이에 가두어진 기름층과 물의 계면의 교란에 대하여 고찰하였다. 와류는 전부 유벽의 끝에서 발생되는 것으로 간주하였다. 유동장의 해석을 위하여 포텐셜 유동 가정하에 계면을 와 특이점 분포면(vortex sheet)으로 나타내었다. 계면의 형상은 계면에 유한개의 가상의 입자를 설정한 후 그 위치를 추적하여 추하였다. 입자의 속도는 와 분포면에 의해서 유발되는 속도를 Biot-Savart 적분을 통해 구하고 여기에 이동하는 점와류(point vortex)에서 유발되는 속도를 합하여 구하였다. 시간에 대한 와 분포면상의 와도의 변화는 계면에서의 와도 방정식을 해석하여 구하였다. 여러 조건하에서 계산된 결과를 바탕으로 상당한 파고의 계면파가 전부 유벽 하단에서 발생되는 와류에 의하여 생성될 수 있음을 입증하였다. The disturbance of oil-water interface confined between tandem fences caused by a sequence of traveling vortices below the interface is investigated. The traveling vortices are assumed to be those detached from the tip of the fore fence. The potential flow is assumed and the density interface is replaced as a sheet of vortex. The shape of the interface is predicted by tracing a finite number of marker particles placed at the interface. The velocity of the marker particles is determined by the Biot-Savart integral along the vortex sheet plus the contribution from the traveling point vortices. The rate of change of vortex-sheet strength is predicted by using an evolution equation for vorticity. The calculated results obtained for various conditions demonstrate that the large amplitude of interfacial wave following the moving vortek can be generated by the vortices.
Electrowetting : Microfluidic Applications and Electromechanical Theory
강관형 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.12
The capillary force becomes more and more dominant as the scale of a system gets smaller. This is partly because the capillary force is proportional to the surface area of an element, while the other body forces such as the gravity force is proportional to the volume of the element. A proper management of the capillary force and its beneficial usage is desirable in handling microsystems. Recently, the electrical control of contact angle on dielectric substrates or on self-assembled mono layers (which is sometimes called electro wetting or more distinctly electrowetting-on-dielectrics) draws much attention for its potential applications in microfluidic control. By using the electrowetting-on-dielectrics, nano- or microliter volumes of (nearly any kinds of) electrolyte liquids can be controlled very quickly and reversibly with low power consumption. In this talk, several typical applications of the electro wetting will be demonstrated. Then, previous understanding on the electrowetting phenomenon (which relies on the thermodynamic approach) will be described, with mentioning some shortcomings of the thermodynamic approach. Then, the newly established electromechanical approach will be introduced, and its usefulness in analyzing the charge-related wetting problems will be discussed.
원형관내의 액체-액체 계면에 대한 전기습윤 현상의 동적 거동
강관형(Kwan Hyoung Kang),정원영(Won Young Chung) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
The contact angle of a meniscus and a droplet can be controlled by using electrowetting phenomena. We investigated the dynamic aspect of electrowetting for an oil-electrolyte interface formed inside a closed glass tube. A step input voltage is applied and the subsequent motion of the interface is recorded by a high-speed camera. A kind of capillary instability is observed near the three-phase contact line, which could degrade the reliability of device utilizing electrowetting such as electrowetting liquid lens. The dynamics of interface motion for different input voltages and the fluid viscosities are analyzed and discussed based on the experimental results.
Separation of Particles by DC-Dielectrophoresis in Microchannels
Kwan Hyoung Kang(강관형),Dongqing Li 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
In electrokinetic transport of liquid and particles, the dielectrophoretic (DEP) force is also generated inside microchannels by the non-uniform DC electric field formed near an obstacle. The DEP force is proportional to the volume of particles; hence, it can be utilized to separate particles having different sizes. It is shown, for a simple straight channel having a rectangular obstacle, that a particle path is greatly affected near the edge of the block due to the DEP force. The trajectory of particles are predicted numerically, which shows a fairly good agreement to experimental results The method is applied to separate two different sizes of particles in a channel network.
Separation of Particles by DC-Dielectrophoresis in Microchannels
Kwan Hyoung Kang(강관형),Dongqing Li 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
In electrokinetic transport of liquid and particles, the dielectrophoretic (DEP) force is also generated inside microchannels by the non-uniform DC electric field formed near an obstacle. The DEP force is proportional to the volume of particles; hence, it can be utilized to separate particles having different sizes. It is shown, for a simple straight channel having a rectangular obstacle, that a particle path is greatly affected near the edge of the block due to the DEP force. The trajectory of particles are predicted numerically, which shows a fairly good agreement to experimental results. The method is applied to separate two different sizes of particles in a channel network.
Recent Progress in Electrofluidics
Kwan Hyoung Kang(강관형) 한국가시화정보학회 2010 한국가시화정보학회 학술발표대회 논문집 Vol.2010 No.4
Addition of polar additives to a dielectric liquid greatly increases the electrical conductivity. The conductivity is field dependent due to Onsager effect. Non-uniform field induces a non-uniform conductivity distribution. Non-uniform conductivity distribution generates free charge in an electric field (Maxwell-Wagner polarization). Our theoretical model predicts the flow fields and scaling behaviors fairly well.