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수정진동자를 사용한 점탄성 유체의 점성계수와 전단 탄성계수 측정에 관한 이론해석
서용권(Yong Kweon Suh),김영한(Young Han Kim) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.7
Quartz crystal oscillator is frequently used in measuring a very small amount of mass attached to or adsorbed on the surface of an electrode on the quartz plate. The physical principle is that the resonance frequency of the shear vibration of the quartz caused by an applied electric field is a function of the mass. Recently, effort has been tried to measure physical properties of viscoelastic fluids, such as viscosity and shear modulus. This paper presents useful formula that can be used in estimating the properties of viscoelastic fluids. Important finding in this analysis is that the formula can produce multiple values for the physical properties of the viscoelastic materials.
허영근(Young Gun Heo),전영훈(Young-Hun Jeon),서용권(Yong Kweon Suh) 한국가시화정보학회 2010 한국가시화정보학회지 Vol.7 No.2
In this paper we report the method of visualizing and measuring the fluid flow within a small droplet of millimeter size. We use a vertical laser sheet in visualization of the micrometer size and special attention is given to the arrangement of microscope to obtain clear images. Then we use a PIV technique to measure the velocity of the internal flow from the images taken. Since the droplet is of spherical shape, the images represent highly deteriorated picture of the real objects due to the refraction phenomenon. In order to compensate the refraction, we in this study developed two kinds of methods for the real velocity. In the first method, the refracted images are directly used to obtain the velocity in the image space, and then the velocity is transformed to the real space. In the second method the images are first transformed to the real-space objects, and then the PIV is used to measure the velocity field. We compared the two results to prove the usefulness of the compensation technique.
Mixing in a Microchannel by using Induced-charge Electro-osmosis
전영훈(Young Hun Jeon),허영근(Young Gun Heo),정원혁(Won Hyuk Jung),수레수 알라파티(Suresh Alapati),서용권(Yong Kweon Suh) 한국가시화정보학회 2010 한국가시화정보학회지 Vol.8 No.4
This paper presents an experimental study on the performance of a micro-mixer using AC electro-osmotic flow. The microchannel is made of PDMS for the side and top walls and glass patterned with ITO for the bottom wall. We first investigated the effect of the applied potential as well as the frequency on the slip velocity. We have found that the slip velocity is roughly proportional to the applied voltage in line with the Helmholtz-Smoluchowski equation and there is an optimum frequency at which the slip velocity becomes maximized. To find the optimum parameters for mixing device we tested our device for various design parameters. It turned out that the best mixing effect is obtained approximately when the electrode angle is 30°, electrode width 200 ㎛, and the frequency of power supply 700 ㎐.
허영근(Young Gun Heo),서용권(Yong Kweon Suh) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In this paper we report the method of visualizing and measuring the fluid flow within a small droplet of millimeter size. We use a vertical laser sheet in visualization of the micrometer size and special attention is given to the arrangement of microscope to obtain clear images. Then we use a PIV technique to measure the velocity of the internal flow from the images taken. Since the droplet is of spherical shape, the images represent highly deteriorated picture of the real objects due to the refraction phenomenon. In order to compensate the refraction, we in this study developed two kinds of methods for the real velocity. In the first method, the refracted images are directly used to obtain the velocity in the image space, and then the velocity is transformed to the real space. In the second method the images are first transformed to the real-space objects, and then the PIV is used to measure the velocity field. We compared the two results to prove the usefulness of the compensation technique.
CFX 코드를 사용한 비정상 DC 전기삼투 유동 해석기법 개발
허영근(Young Gun Heo),전영훈(Young Hun Jeon),정종현(Jong Hyeon Jeong),서용권(Yong Kweon Suh) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In this study, we couple a commercial code, ANSYS CFX and Fortran codes for solving electro-osmotic flows around a pair of electrodes receiving DC potentials attached to the top and bottom walls of a rectangular domain. Up to now, no work has been presented in the literature which obtained the solutions of the electro-osmotic-flow problems by using the CFX. Difficulties in this techniques are: Firstly, the ion transport equations (i.e., Nernst-Planck equations) must be solved by using the general transport equation provided by CFX, but in most often there is numerical instability in treating the source terms. Secondly, to calculate the source term we need to evaluate the electric field which must be obtained from a separate Fortran code in terms of the potential which is given from the solution of the Poisson equation. In this case, care must be given to the computer-memory problem. In this study, we develop a module of Fortran programs which are used in solving the ion transport problem in coupling with the CFX. We will present how the developed code is applied to solving the dc electro-osmotic problem within a simple geometry. We also address various problems encountered during the development process and explain how such problems are tackled.
외부 가스 유동에 의한 미소 액적 내부 유동 제어 및 가시화
허영근(Young Gun Heo),허효원(Hyo Weon Heo),전영훈(Young Hun Jeon),서용권(Yong Kweon Suh) 한국가시화정보학회 2010 한국가시화정보학회 학술발표대회 논문집 Vol.2010 No.11
We conducted experimental visualization and numerical simulations of flow inside a droplet subjected to an external gas flow. The purpose of this study is to confirm a flow-control method provided by agas flow over a droplet, which may be used in the enhancement of the semiconductor performance, in the case where the semiconductors are manufactured by the principle of inkjet printing. Our ultimate target is to remove the coffee-stain effect and make the osc align in the direction of current in between a pair of micro electrodes.
박재현(Jae Hyun Park),서용권(Young Kweon Suh) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
In this paper, we present that flow and heat transfer characterisitics of oscillatory impingging jet which have been numericlly invastigated using parallel computations, Numenerical value were obtained for dimensionless distance H=4, dimensionless outlet length L=45 and Reynolds number Ro=1500. It was found that the oscillatory impingging jet generated the regular heat transfer area even though the maximum heat transfer is lower than nonoscillatory impingging jet. We also found that heat transfer depends on the period of nozzle for the oscillatory imqingging jrt.
원형 실린더가 있는 직사각형 용기내의 스핀-업 유동에 관한 실험 및 수치해석
박재현(Jae Hyun Park),서용권(Young Kweon Suh),김성균(Sung Kyun Kim),손영락(Young Rak Son) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
This paper describes a study of the spin-up of a free-surface fluid in a rectangular container in which an internal cylindrical obstacle is mounted. Experiments and numerical analysis have been carried out for a variety of obstacle position. Increase in the speed of background rotation and near wall position of cylindrical obstacle results in the complex flow structures. Numerical and experimental results agree well with each other and the Ekman-pumping model is also applied to this flow.
래티스-볼츠만 법을 이용한 T-채널 내의 이상유동에 대한 수치해석적 연구
박재현(Jae Hyoun Park),서용권(Young Kweon Suh) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
This study describes a simulation of two-dimensional bubble forming and motion by the Lattice Boltzmann Method with the phase field equation. The free energy model is used to treat the interfacial force and deformation of binary fluids system, drawn into a T-junction the micro channel. A numerical simulation of a binary flow in a T channel is carried out by using the parallel computation method. The aim in this investigation is to examine the applicability of LBM to numerical analysis of binary fluid separation and motion in the micro channel.
Lattice Boltzmann 법 및 병렬 연산을 이용한 마이크로 채널 내의 Binary flow에 관한 수치해석적 연구
박재현(Jae Hyoun Park),서용권(Young Kweon Suh) 한국마린엔지니어링학회 2006 한국마린엔지니어링학회 학술대회 논문집 Vol.2006 No.-
This study describes a simulation of two-dimensional bubble forming and motion by the Lattice Boltzmann Method with the phase field equation. The free-energy model is used to treat the interfacial force and deformation of binary fluids system, drawn into a T-junction the micro channel. A numerical simulation of a binary flow in a cross-junction channel is carried out by using the parallel computation method. The aim in this investigation is to examine the applicability of LBM to numerical analysis of binary fluid separation and motion in the micro channel.