磁場의 영향을 받는 Czochralski 유동장에 관한 수치적 연구

김창녕 慶熙大學校 1992 論文集 Vol.21 No.-

均一한 磁場이 Czochralski 도가니에 가하여졌을 때의 溫度場과 流動場이 數値的으로 연구되었다. 여기에서 온도차이에 의한 浮力, 自由表面에서의 반경방향으로의 온도구배로 因한 thermocapillarity, 도가니와 結晶의 회전으로 인한 遠心力및 외부에서 걸러준 磁場에 의한 磁性力등이 Czochralski 유동장을 지배하고 있다. 회전방향으로의 對稱性으로부터 자오평면 (meridional plane) 에서의 속도성분과 회전방향의 속도성분이 구하여졌으며 온도, 압력, 電位등이 해석되었다. 磁場의 영향아래에서의 Czochralski 流動場에서는 회전방향의 속도성분이 電位의 구배를 惹起시키고 있는데 이러한 회전방향의 속도성분을 대류작용에 의하여 도가니벽에서부터 자유표면을 다라 결정표면의 아래까지 전달되어 현저하게 나타난다. 또 이러한 회전방향의 속도성분을 結晶표면의 아래에서 큰 반경방향으로의 압력구배를 만들어주고 있다. 磁場의 세기가 큰 경우에 모든 속도성분이 작아지고 있으며 결정표면 아래에서 압력구배가 작아진다. 이와 같이 磁場의 영향아래에서의 Czochralski 유동장의 이해하게 되면 受動性을 갖는 solute의 濃度에 관한 擧動을 把握할 수 있게 될 것이다.

경사진 자장의 영향을 받는 관안에서의 자기유체유동

김창녕 金烏工科大學校 1990 論文集 Vol.11 No.-

A numerical procedure ws devised to predict the characteristics of the flow field in a liquid metal magnetohydrodynamic(MHD) flow. By the use of the procedure, a steady-state, incompressible, viscous, three-dimensional MHD flow under the influence of a magnetic field applied obliquely at an angle of 45˚ to each side wall of a rectangular duct has been studied at an extremly low magnetix Reynolds number by means of a finite volume method. The use of the control volume approach enables the implementation of the corrective step based on the fluid flux across the face of the volume, which contributes to convergence and physical accuracy. Numerical results shows that the axial velocities are large on the diagonal region of the cross-section lying parallel to the magnetic field with the peak velocities located at the corners.

장방형관에서의 자기유체유동

김창녕 金烏工科大學校 1991 論文集 Vol.12 No.-

In order to simulate flows in an MHD pump, a three-dimensional, steady-state, incompressible, liquid metal magnetohydrodynamic(MHD) flow has been investigated under the influence of applied magnetic and electric fields. Governing equations including the viscous and inertial effects are solved by means of the finite volume method. At an intermediate interaction parameter and Hartmann number, the distributions of axial velocity, pressure and electric current are obtained under, the assumption that magnetic Reynolds number is very small. In the vicinity of electrodes, the axial velocity distribution is generally flatted and the velocities near the electrodes become larger, yielding M shape profile. Here, the velocity gradients near the duct walls are very steep, forming side layers and Hartmann layers. As the fluid passes the electrodes, the pressure becomes lager and the peculiar pressure behavior near the edge of the electrodes is seen. The transverse electrical currents are concentrated in the Hartmann layers. This study has shown the intrinsic three-dimensional effect of the MHD flow which was not reported yet by one-.and two- dimensional approaches.

아래면에서 가열되는 채널의 혼합대류 현상에 관한 수치해석 연구

김현수,김창녕 경희대학교 산학협력기술연구원 1996 산학협력기술연구논문집 Vol.2 No.-

A study is carried out on the mixed convection in two types of channel that are heated from below. Mixed convection in channels can be seen in many environmental devices such as energy storage systems, cooling devices of microelectronic equipments. Steady-state, two-dimensional, incompressible flows in channels with different wall temperatures are considered. Governing equations include the continuity equation, momentum equation and energy equation. Finite volume method was employed for the discretization and SIMPLER algortithm was used for calculating pressure term. TDMA associated with line by line method is used for iterative calculation of each equation. The result shows the transition of flow patterns from pure forced convection to pure natural convection and it can be seen that as the convective effects diminishes, the natural convection cell number increases that depends on the aspect ratio as well as boundary condition of side walls.

초크랄스키 실리콘 단결정 성장에 미치는 커스프 자기장의 효과

김창녕,이제희 慶熙大學校 材料科學技術硏究所 1997 材料科學技術硏究論集 Vol.10 No.-

The charcteristics of melt flows, temperatures and concentrations of oxygen are numerically studied for various intensities of cusp magnetic fields in the Czochralski furnace. Cusp magnetic fields can suppress buoyancy force due to the heating of crucible wall and centrifugal force due to the rotations of the crucible and crystal. As the magnetic fields are increased, velocities of the flow are greatly diminished, the average oxygen concentration is lowered and the radial uniformity of oxygen concentration at melt/crystal interface is improved.

Misaligned된 비균일 자장이 인가된 초크랄스키 유동특성에 대한 수치적 해석

김창녕 慶熙大學校 材料科學技術硏究所 1999 材料科學技術硏究論集 Vol.12 No.-

Flow Characteristics have been analyzed numerically in the process of Czochralski single crystal growth of silicon under the influence of misaligned cusp magnetic fields. Since the silicon melt in a crucible for crystal growth is of high temperature and of highly electrical-conducting, experimentation method has difficulty in analyzing the behavior of the melt flow. A set of simultaneous nonlinear equations including Navier-Stokes and Maxwell equations has been used for the modelling of the melt flow which can be regarded as a liquid metal. Together with the melt flow which forms the Marangoni convection, a flow circulation is observed near the corner close both to the crucible wall and the free surface. The melt flow tends to follow the magnetic lines instead of traversing the lines. These flow characteristics helps the flow circulation exist.

Extrusion Heat Sink에서의 열전달에 관한 수치해석적 연구

김창녕,문성일 慶熙大學校 材料科學技術硏究所 1998 材料科學技術硏究論集 Vol.11 No.-

A numerical study has been carried out on the evaluation of performance of extruded heat sink in electronic equipment. Heat transfer characteristics have been analyzed for various design parameters including the shape of heat sink, thickness of fin base and fin pitches. A commercial program called Flotherm has been employed for the numerical calculation. Optimal design of the heat sink has been persued which is closely related with the reduction of heat resistance involved in conduction and convection of heat.

실내내장재에서 방출되는 VOCs 거동의 모델링

신동민,김창녕 경희대학교 환경연구소 2002 環境硏究 論文集 Vol.11 No.-

A numerical modelling was developed to predict the volatile organic compounds(VOCs) emitted from indoor material in the experimental apparatus. Previously the mass diffusion coefficient of VOCs in the indoor materials, the mass/air partition coefficient, and the initial concentrations in the indoor materials were obtained from the experimental. Modeling considers the mass transfer process within the indoor materials and in the air region. In the present study the predictions by the current modelling were validated by a Computational Fluid Dynamics(CFD) technique and VOCs concentration distribution in the calculation domain was predicted with time. Predicated VOCs concentration are similar to that of the experimental result.

열전달에 의한 Gas Stirred Liquid Bath 내의 유동특성에 관한 연구

최정렬,김창녕 경희대학교 산학협력기술연구원 1998 산학협력기술연구논문집 Vol.4 No.-

The flow and temperature fields in Gas Stirred Liquid Bath Systems were numerically analyzed to predict flow characteristics under the influence of heat transfer. Eulerian-Eulerian approach was used for the formulation of both the continuous and dispersed phases. Turbulence in the liquid phase was modeled using a two-equation κ-ε model. Interphase friction and heat transfer coefficients were calculated by using correlations available in the literature. The modification of the general purpose computer program PHOENICS code was employed to predict the mean flow fields, volume fraction and temperature fields. Turbulence dispersion of the phases was modeled by introducing a "dispersion Prandtl number". The calculated results were compared with experimental measurements. Quantitatively it shows very satisfactory agreement with experimental results for almost regions of ladle. The results are of interest in the design and operation of wide variety of material processing.

A Structural Analysis on the Leaflet Motion Induced by the Blood Flow for Design of a Bileaflet Mechanical Heart Valve Prosthesis

Young Joo Kwon,Chang Nyung Kim,Jae Won Lee 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.9

This paper presents a structural analysis on the rigid and deformed motion of the leaflet induced by the blood flow required in the design of a bileaflet mechanical heart valve (MHV)<br/> prosthesis. In the study on the design and the mechanical characteristics of a bileaflet mechanical heart valve, the fluid mechanics analysis on the blood flow passing through leaflets, the kinetodynamics analysis on the rigid body motion of the leaflet induced by the pulsatile blood flow, and the structural mechanics analysis on the deformed motion of the leaflet are required sequentially and simultaneously. Fluid forces computed in the previous hemodynamics analysis on the blood tlow are used in the kinetodynamics analysis on the rigid body motion of the leaflet. Thereafter, the structural mechanics analysis on the deformed motion of the leaflet follows to predict the structural strength variation of the leaflet as the leaflet thickness changes. Analysis results show that structural deformations and stresses increase as the fluid pressure increases and the leaflet thickness decreases. Analysis results also show that the leaflet becomes structurally weaker and weaker as the leaflet thickness becomes smaller than 0.6 mm.