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유신오,박정우,서이수 동아대학교 생산기술연구소 1999 生産技術硏究所硏究論文集 Vol.4 No.1
In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, vorticity, internal angular momentum and induced magnetization as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter and we theorefically analyze characteristic of induces magnetization as the magnetic response.
유신오(S. O. Ryu),박정우(J. W. Park),최병호(B. H. Choi),서이수(L. S. Seo) 한국자기학회 2000 韓國磁氣學會誌 Vol.10 No.1
In the present work, we analyze theoretically the flow of magnetic fluids in a circular pipe with longitudinal magnetic field. We used governing equations induced Shliomis and Polar theory of Eringen. Using theoretical equations and distributions for the velocity, vorticity and angular velocity as the magnetic response, it is shown that magnetic fluid flow is non-Newtonian fluid. We investigate dynamic characteristic of magnetic fluid by comparing longitudinal magnetic field with transverse magnetic field. And, the limits, influence magnetic fluid, of the intensity of the magnetic field with polar, size and magnetic effect parameters are shown.
홈으로 된 내부형상이 Taylor Vortex 형성에 미치는 영향
유신오,승삼선 三陟大學校 1997 論文集 Vol.30 No.1
We have used the technique of visualization to study influences on Taylor vortex flow formation in a fluid contained between concentric cylinders with grooved shape of inner cylinder. Where the inner cylinder is rotating. So we found that radius ratio and aspect ratio have an effect on flow structures and processes from laminar Taylor vortex to turbulent Taylor vortex. The results of this experimental study are as follows : 1) In laminar Taylor vortex, a radius ratio has an effect on width of cells by rotating inner cylinder with grooved shape. So cell's width of grooved section is wider than its of straight shape. 2) Aspect ratio according to width of groove has an effect on axis of cell to which is leaned over each side of groove. Especially the number of grooves and the ratio of aspect ratio in total straight shape to aspect ratio in grooved shapes play a important role in leanings towards axis of cell in grooved section. 3) In high speed, grooved sections in an inner cylinder play a role in delaying fully developed turbulence except itselves. And it related with radius ratio. 4) In turbulent Taylor vortex, effects of aspect ratio which is effected on axis of cell which is leaned over each side of groove are disappeared. But effects of radius ratio which are caused cell's width of grooved section is wider than straight shape are still appeared.
유신오,박정보,조석수 三陟大學校 1999 論文集 Vol.32 No.1
The postion and the length of surface micro-crack has random properties. It is difficult to detect the progressive changes in surface micro-crock distribution that occur during fatigue stressing. In this paper to overcome this problem, fractal dimension was introduced to characterize the change in two-dimensional surface micro-crack distribution during fatigue process. Box counting method was adopted to measure the fractal dimension. The features of surface micro-crack growth and coalescence have fractal property. Fractal dimension increases with number of cyclic load. Remaining fatigue life of mechanical components can be predicted by the relation between fractal dimension and cycle ratio to fracture. Therefore, we proposed complex system design that uses fractal dimension in material design and structure design and safety estimation.
유신오,승삼선 三陟大學校 1996 論文集 Vol.29 No.1
In this review, we have researched vehicle design considering aerodynamic concepts. Especially under high speed conditions, aerodynamic concepts play an important role in vehicle design. And we know that optimization method of each part in producted vehicles introduced by Hucho et al. is very useful. Therefore nowadays we must try to design vehicle styling and optimization method of each part in the futrue cars. Also in today's competitive environment there is a need to create a synergy effect between the EFD(Experimental Fluid Dynamics) and CFD(Computational Fluid Dynamics) process.
경사진 내부 원통의 형상비 변화에 따른 Taylor Vortex에 대한 실험적 연구
유신오,승삼선 三陟大學校 1996 論文集 Vol.29 No.1
We have used the technique of visualization to study the formation and extinction of Taylor vortex flow in a fluid contained between concentric cylinders with the ramped rotating inner cylinder. Where the ramped inner cylinder means the different aspect rating. compared with straight inner cylinder. And we focus how the ramped inner cylinder play a role in formation and extinction of Taylor vortex flow. The results of this experimental study are follows 1) In low speed, zigzag type cells form in the sub-critical section during formation of Taylor vortex flow. But the ramped section in an inner cylinder prohibit zigzag type cell from formation in the super-critical staight section. 2) In high speed, ramped section in an inner cylinder play a role in promoting turbulent Taylor vortices. 3) We assume that some bifurcation occurred during process from Taylor vortex flow to fully-developed turbulent flow. 4) In the R=6370, turbulent Taylor vortices exist in a straight inner cylinder. But in a ramped section with inner cylinder, Taylor vortices expire and fully-developed turbulent flow exists.