韓國農村家庭의 醫療實態

金性初,盧忍圭 대한의학협회 1976 대한의학협회지 Vol.19 No.9

反應이 있는 亂流에서 擴酸, 消散 및 壓力- 速度의 相關關係 解析

金星初 順天大學校 1989 論文集 Vol.8 No.1

熱放出性이 큰 反應이 있는 亂流에서 變動포텐셜과 過度場 사이에 중요한 相關關係가 있는지 與否가 분명하지 않으며, 純粹한 過度動力學처럼 전통적인 亂流槪念을 적용할 수 있는지 조사해야 한다. 勾配擴散 模型은 반응이 있는 난류의 極端的인 해결 방법으로 적용은 간단하지만 모형 자체가 深刻한 誤差를 갖을 수 있으므로 火焰 및 燃燒形態에 따라서 適當히 修正되어야 한다. 또한 消散은 非壓縮性 흐름에 대한 경우와 비교해서 전적으로 새로운 形態를 갖을 수 있다. 壓力一速度의 相互作用은 燃燒器에서 처럼 壓力場이 一定하지 않은 때는 그렇지 않은 경우에 비교하여 다른 특성을 갖는다. 난류문제는 연소현상의 有無에 관계 없이 實驗,理論 또는 數値硏究에 많은 어려움이 있다. 즉, 거의 모든 自然現象이 난류현상임에도 불구하고 해석에 많은 가정이 따르고 현상마다 다르다. 한편, 電子計算器의 큰 발전과 數値解法의 개발로 많은 문제들이 해결되고 있으나 이에 앞서서 실험에 의한 자료 확보와 연구가 폭넓고 깊이 이루어져야 한다. In general, turbulent modellings agree well with the experimental results for the cold gas without exothermicity. However, they can not be applied to the turbulent reacting problems as it is. A concept of the gradient diffusion accepted in the turbulent reacting problems is very simple to use but contains large errors. And the form of reacting turbulent dissipation is very different from that in the cold gas cases. Pressure-velocity correlation is hard to measure experimentally and must be carefully dealt with in the flow field where the pressurd is not uniform, e.g.inside of combustor. This paper describes analytically based on the physical concept diffusion, dissipation and pressure-velocity correlation in the reacting turbulent flow.

패널 방법과 불연속 와류 입자방법에 의한 2차원 무딘 물체 주위의 비정상 공력 해석

김성초 순천대학교 공업기술연구소 1998 工業技術硏究所論文集 Vol.12 No.-

This paper describes the describes the discrete vortex method to solve a two-dimensional incompressible flow field around bluff bodies such as triangle and square prisms. This method is combines with the panel method since the governing equation is reduced to Laplace equation. Vortices generated from the known separation points are mathematically treated by a solid and free vortex model with introducing a cut-off radius. And the exponential type of vortex diffusion is assumed. Reynolds numbers are 12400 and 17500, and angles of attack are o° and 5° for triangle and square prisms, respectively. The Strouhal numbers characterizing the vortex shedding rate are 0.138 and 0.123, and the drag coefficients are 2.3 and 2.1 for triangle and square prisms, respectively. Thus the computational results are reasonably acceptable comparing with experimental ones. In addition, the position of wake vortices shed from the separation points are traced.

원통 주위의 비정상 비압축성 층류 흐름의 수치해석

김성초 順天大學校 1997 論文集 Vol.16 No.1

This paper describes the marker-and-cell method(MAC) to calculate two-dimensional unsteady laminar flow around the circular cylinder. The governing equations are expressed in the conservative forms and the pressure field is evaluated by the Poisson equation with the successive over-relaxation method. The grid system is generated simply by the conformal mapping function and the primitive physical variables are computed at the different cell points, i.e., the grids are staggered. It is found that this numerical procedures is successful to solve the unsteady and separated flow occurred around the blunt body. The numerical results show the pressure, velocity vector and streamline distributions, and ad hoc the confined and shedding vortices behind a circular cylinder. There is periodic behavior in lift coefficient, however, drag characteristics has no strong periodicity.

3차원 와 격자 해석에 의한 날개의 공기역학적 특성

김성초 순천대학교 공업기술연구소 1993 工業技術硏究所論文集 Vol.7 No.-

This paper analyzes the aerodynamic characteristics of the various wings using the vortex lattice method(VLM) based on the potential flow theory. VLM calculates the lift coefficient and its slope with respect to the angle of attack(a) for the various shape of wing and aspect ration(AR), i.e., forward or backward swept wings, tapered wings and delta wings. The numerical results agree well with the existing experimental ones in the favorable range of angle of attack, however the discrepancy between them is caused by the real fluid properties. VLM can be easily extended to analyze the aerodynamic characteristics of geometrically complex three-dimensional bodies such as airplanes, cars and so on.

2차원 물체 주위의 유동장에 대한 쌍곡선형 격자 생성

김성초 順天大學校 1993 論文集 Vol.12 No.1

This paper describes the hyperbolic grid generation procedures around an ellipse and an airfoil. Two condetions, the orthogonality of grids and the concentrically circular grid cell area, are adopted to constitue the governing equations, which can be solved efficiently by the implicit method called block-elimination of Keller box method. We include the fourth order dissipation damping term in the finite difference equations to guarantee the stability of solution. This method is applicable to any other two- dimensional geometries, and also extendible to three- dimensional bodies.

익형에서의 천음속 유동

김성초 순천대학교 공업기술연구소 1989 工業技術硏究所論文集 Vol.3 No.-

It is recognized in recent years that the flight in transonic speed range is important from safe and economic points of view. Transonic flight is essentially related to the shock wave occurred on the wing, which induces the flow separation, i.e. stall. Since this phenomena is very complex physically and mathematically, the research to solve the transonic flow is much restricted. However, we can hope to find the solution with very high speed computer and well developed numerical method based on mathematics. This paper describes the analytic method and physical characteristics for the transonic flow on the airfoil.

석유 가스 과정에서 유량 제어 밸브를 닫을 때 관에서의 압력 및 유량의 변화

김성초 순천대학교 공업기술연구소 1995 工業技術硏究所論文集 Vol.9 No.-

This paper describes the pressure and flow rate variation due to closing the control valve suddenly which is located at the end of the pipe attached to the storage tank of liquefied petroleum gas. It is important to determine the valve closing time which affects the safety of pressure tank-pipe system since the water hammering may occur by the rapid valve stroking. It is necessary to analyze the compression wave motion in this phenomena, thus the governing equation becomes hyperbolic type and that can be solved by the characteristic method. In this research, two cases are calculated, i.e., the valve closing time and the maximum pressure at the pipe and are specified respectively. When the valve is closing maximum pressure is induced at the pipe end, and the flow rate is rapidly decreased to zero as time goes on regardless of cases. The pressure inside the pipe increases all of a sudden when the valve begins to be closed. Maximum pressure becomes twice as much as that of the storage tank. The pressure at certain locations increases slightly until the valve is completely closed when the valve time is specied, in the other hand, it remains constant when maximum pressure at the pipe end is specified. Especially the irregular pressure variation is found along the pipe at the beginning of the valve closing.

용기와 관으로 구성된 수처리 장치에서 압력 수두 및 유량 변화와 자유 진동 현상

김성초,김기성 순천대학교 공업기술연구소 1996 工業技術硏究所論文集 Vol.10 No.-

This paper describes the pressure head - flow rate variation and free vibration phenomena in the tank - pipe systems which is a simple model of the water treatment. The system consists of the storage tank and serial connection pipes with the different diameters and lengths. When the flow is controlled by the valve attached at the end of pipe, the pressure at this end is excessively large and shows small oscillation comparing that of tank, and the flow rate decreases to zero monotonically as time goes by. In the primary mode shape obtained by the free vibration analysis, the amplitude of pressure is 6 - 7 times of the tank pressure, and that of flow rate is about 12% of the normal state. Especially the phase of pressure is more delayed by ½π radian than that of flow rate.

비압축성 2차원 층류 유동에서 임계층에 대한 비선형 해석

김성초 순천대학교 공업기술연구소 1992 工業技術硏究所論文集 Vol.6 No.-

This describes the phenomena near the critical layer for the stratified laminar shear layer, the Rossby wave and the gravity wave based on the celebabted Orr-Sommerfeld(O-S) equation which expresses the stability of flow. It is possible to solve the O-S equation numerically provided that the velocity of main flow, and the initial and boundary conditions are given reasionably. However we can not easily find the physical meaning of the flow characteristics from those numerical solutions. So it is valuable to develop the mathematical perturbation solution procedure near the interesting region, i.e. the critical layer, though that is difficult and lengthy. The stability of the stratified shear layer depends on the Richardson number(Ri), and Ri is 1/4 at the neutral state. The small disturbance(ε) forced in the stratified shear layer has the nonlinearity with the time scale of O[(1/4-Ri)^(-1)] and its time scale is O(ε^(-4/7)). When the oscillation of the periodic function is forced, the discontinuity in the vorticity occurred near the critical layer is O(ε^(1/2)). The critical layer in the gravity wave, │y│《1, absorbs, reflects or transmits the wave energy according to the wave number and Richardson number. Eventually, we should analyze numerically the O-S equation for the specified flow because it is difficult to find the general solution of it. The time scale etc. based on the theoretical analysis and experiments is necessary to find out the transition phenomena which is unsteady state.