• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.727-732
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• 2001

The purpose of this study is to compare the time mean velocity distribution, the time mean kinetic energy, and the time mean turbulence intensity between vertical and horizontal flow fields in a coaxial circular pipe by PIV measurement. Experiments are performed at a Reynolds number 2,000, measuring regions divided as the section regions A, B, C, D in flow fields. The angle of the high-frequency ultrasonic is selected in the direction of $45^{\circ}$ to the flow axes and it is reflected several times. In results, it is clarified that the effect of gravity is given in the vertical flow field compared with the horizontal flow field and the ultrasonic affects the turbulence enhancement. And kinetic energy and turbulence intensity with ultrasonic are shown slightly bigger than those in flow field without it.

• Bulletin of the Korean Chemical Society
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• 제22권4호
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• pp.337-348
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• 2001

This article gives an overview of a recently developed channel system, frit-inlet asymmetrical flow field-flow fractionation (FI-AFlFFF), which can be applied for the separation of nanoparticles, proteins, and water soluble polymers. A conventiona l asymmetrical flow FFF channel has been modified into a frit-inlet asymmetrical type by introducing a small inlet frit near the injection point and the system operation of the FI-AFlFFF channel can be made with a great convenience. Since sample components injected into the FI-AFlFFF channel are hydrodynamically relaxed, sample injection and separation processes proceed without interruption of the migration flow. Therefore in FI-AFlFFF, there is no requirement for a valve operation to switch the direction of the migration flow that is normally achieved during the focusing/relaxation process in a conventional asymmetrical channel. In this report, principles of the hydrodynamic relaxation in FI-AFlFFF channel are described with equations to predict the retention time and to calculate the complicated flow variations in the developed channel. The retention and resolving power of FI-AFlFFF system are demonstrated with standard nanospheres and protreins. An attempt to elucidate the capability of FI-AFlFFF system for the separation and size characterization of nanoparticles is made with a fumed silica particle sample. In FI-AFlFFF, field programming can be easily applied to improve separation speed and resolution for a highly retaining component (very large MW) by using flow circulation method. Programmed FI-AFlFFF separations are demonstrated with polystyrene sulfonate standards and pululans and the dynamic separation range of molecular weight is successfully expanded.

• 한국대기환경학회지
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• 제12권3호
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• pp.243-254
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• 1996

The main purpose of this study is to investigate the collection efficiency characteristics of a cylindrical ESP. To do that, it is necessary to analyze the electric field, gas flow field, and mechanism of particle movement by numerical simulation based on EHD model. For a gas flow field, Navier-Stokes equation involving the electric source term was solved by SIMPLE algorithm. In case of the electric field, the current continuity and electric field equations were solved by S.O.R. method. The analysis of particle movement was performed on the basis of PSI-CELL model from the Lagrangian viewpoint. The results showed that the influence on the gas flow field by the electric field is almost negligible in a cylindrical ESP. The particle drift velocity $V_P$ toward the collection surface is increased continuously by the electrostatic force due to the rise of particle charge as the particle is moving to the flow direction and the particle size becomes larger. The collection efficiency is to quitely higher with the increase of applied voltage for the same particle size, while becomes smaller as the inlet velocity is increased.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.208-217
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• 1999

The present work describes the prediction method for the unsteady flow field and the acoustic pressure field of a ducted axial fan. The prediction method is comprised of time-marching free-wake method, acoustic analogy, and the Helmholtz-Kirchhoff BEM. The predicted sound signal of a rotor is similar to the experiment one. We assume that the rotor rotates with a constant angular velocity and the flow field around the rotor is incompressible and inviscid. Then, a time-marching free-wake method is used to model the fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The newly developed Helmholtz-Kirchhoff BEM for thin body is used to calculate the sound field of the ducted fan. The ducted fan with 6 blades is analysed and the sound field around the duct is calculated.

• Journal of applied mathematics & informatics
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• 제41권2호
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• pp.401-411
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• 2023

The effects of longitudinal velocity dusty fluid flow in a weak magnetic field are investigated in this paper. An external uniform magnetic field parallel to the flow of dusty fluid influences the flow of dusty fluid. Besides that, the problem under investigation is completely defined in terms of identifying parameters such as longitudinal velocity (u), Hartmann number (M), dust particle interactions β, stock resistance γ, Reynolds number (Re) and magnetic Reynolds number (Rm). While using suitable transformations of resemblance, The governing partial differential equations are transformed into a system of ordinary differential equations. The Hankel Transformation is used to solve these equations numerically. The effects of representing parameters on the fluid phase and particle phase velocity flow are investigated in this analysis. The magnitude of the fluid particle is reduced significantly. The result indicates the magnitude of the particle reduced significantly. Although some of our numerical solutions agree with some of the available results in the literature review, other results differs because of the effect of the introduced magnetic field.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.139-143
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• 2003

In this study the numerical analyses on cavity flow in supersonic flow field are conducted. According to the length-to-depth ratio of cavity, the shear layer is changed, consequently influencing on vortex structure inside the cavity. Especially in case the fluid flow outside cavity impinges inside the cavity, the oscillation of the cavity flow is identified. Another result is that though the cavity flow shows the unsteadiness, characteristics of cavity flow can be represented by pressure coefficients converged.

• 대한기계학회논문집B
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• 제33권9호
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• pp.666-673
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• 2009

The turbulent swirling flow field characteristics of a gun-type gas burner with a combustion chamber were investigated under the cold flow condition. The velocities and turbulent quantities were measured by hot-wire anemometer system with an X-type probe. The turbulent swirling flow field in the edge of a jet seems to cause a recirculation flow from downstream to upstream due to the unbalance of static pressure between a main jet flow and a chamber wall. Moreover, because the recirculation flow seems to expand the main jet flow to the radial and to shorten it to the axial, the turbulent swirling flow field with a chamber increases a radial momentum but decreases an axial as compared with the case without a chamber from the range of about X/R=1.5. As a result, these phenomena can be seen through all mean velocities, turbulent kinetic energy and turbulent shear stresses. All physical quantities obtained around the slits, however, show the similar magnitude and profiles as the case without a chamber within the range of about X/R=1.0.

• Wind and Structures
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• 제4권4호
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• pp.333-352
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• 2001

A two dimensional discrete vortex method (DIVEX) has been developed to predict unsteady and incompressible flow fields around closed bodies. The basis of the method is the discretisation of the vorticity field, rather than the velocity field, into a series of vortex particles that are free to move in the flow field that the particles collectively induce. This paper gives a brief description of the numerical implementation of DIVEX and presents the results of calculations on a recent suspension bridge deck section. The predictions for the static section demonstrate that the method captures the character of the flow field at different angles of incidence. In addition, flutter derivatives are obtained from simulations of the flow field around the section undergoing vertical and torsional oscillatory motion. The subsequent predictions of the critical flutter velocity compare well with those from both experiment and other computations. A brief study of the effect of flow control vanes on the aeroelastic stability of the bridge is also presented and the results from DIVEX are shown to be in accordance with previous analytical and experimental studies. In conclusion, the results indicate that DIVEX is a very useful design tool in the field of wind engineering.

• 지질공학
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• 제28권3호
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• pp.341-348
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• 2018

Landslides can be caused by localized intense rainfall. The loss of human lives and damage to property from landslides is increasing. However, little information exists on the movement and flow of sediment material at the time of rapid landslides. In this study, a field survey was conducted of landslides that occurred in 2013 in the Hadari area of Yeoju city in Korea. This was followed by numerical analysis. The purpose is to analyze the characteristics of a consequent debris flow and its movement at the time of failure. The results of the field survey and numerical analysis are consistent with each other. The maximum velocity of the debris flow was ~9.335 m/s and the maximum sediment thickness ~4.674 m. The latter is similar to the traces of debris flow observed in the field.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.3-6
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• 2002

In this paper, the electrolyte flow treatment is suggested using together with needle and magnet. On account of Lorentz force law, we can not only induce the circulation of body fluids at specific hurt but also apply on the treatment of cell membrane voltage control controlling the electrolyte flow. If electric field is added to human body fluid, electrolyte and then magnetic field is taken by magnet, we can induce local region flow through needle, global region flow with artificial electrical field and magnetic field. Electrolyte flow is excellent treatment in clinical treatment.