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이병서(Byoung Seo Lee),이준식(Joon Sik Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
A computer program based on computational fluid dynamics has been developed for simulation of EHD induction pumping. An equation formulated for electric potential as the dependent variable is used, which removes the ambiguity of boundary conditions. The program can be applied in nonorthogonal coordinates. The calculations show that the dependency of applied voltage and frequency agrees well with the experiments of Melcher's. Backflows are shown in low frequency regime, which has been reported to have a destructive structure due to unstability in the experiments. In addition, the developments of flows are presented from unsteady simulations.
이병서(Byoung Seo Lee),이준식(Joon Sik Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Computational fluid dynamics simulations are conducted to investigate flow characteristics of a peristaltic micropump. The predicted relation between the pressure head and the flow rate agrees well with experiments. The flow behavior at every space and time, in various viewpoints, seems to be approximated as that in laminar channel flows. The velocity profiles either in the chamber or the channel are much similar to those of the Poiseuille flow. The pressure drops show a proportional relation with the flow rate, which is coincident with the equation derived from laminar flat-channel flows.
극초단 펄스 레이저 가공에서 보로노이 다각형 분석법을 이용한 벌크 용융에 대한 분자동력학적 연구
이병서(Byoung Seo Lee),박승호(Seungho Park),이준식(Joon Sik Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
A molecular dynamics study is conducted on ultrashort pulsed laser ablation, which is expected to be a promising tool for micro/nanoscale fabrication in future industry. The simulations have been conducted for silicon atoms described by the Tersoff model with laser fluences 300 ~ 900 J/m² and pulse durations of 100 fs and 5 ps FWHM. The Voronoi polyhedron analysis is used to investigate bulk melting that has been observed in the simulated results. The Voronoi polyhedron analysis is proved to be an effective tool in many respects for analyzing bulk melting. The relationship between superheating and melting time is derived from the distribution of Voronoi polyhedron properties of the results.
보로노이 다면체 해석을 이용한 액상, 비정질 실리콘 및 비정질화 과정의 구조 해석
이병서(Byoung Seo Lee),이동범(Dong Bum Lee),이준식(Joon Sik Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Structural properties of amorphous and liquid silicon are investigated by the Voronoi Polyhedron analysis. The atomic structures of amorphous and liquid silicon are obtained by molecular dynamics with the Tersoff potential model. The topological properties generated by cutoff radius of 0.33 nanometer establish the difference in the structural characters of the two phases of silicon. The mechanisms in creation and growth of amorphous nuclei are studied by defining and visualizing the amorphous nucleus, which is turned out to be a proper method to the study in the kinetics of phase change.
전기수력학적 유도 마이크로 펌프에 대한 전산유체역학 해석
이병서(Byoung Seo Lee),이준식(Joon Sik Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
A numerical program based on computational fluid dynamics has been developed to simulate characteristics of an EHD induction micropump. The ambiguity of boundary conditions was removed by adopting an equation formulated for electric potential as the dependent variable. The calculations show that the dependency of frequency agrees well with the experiments and the previous analysis. The instability, caused by backflows, is getting stronger as the channel depth increases, which is consistent with experiments. The present study reveals that it is due to the limit in the penetration depth which the electric field can affect. Despite the disadvantage of large channel depth, there is a certain optimal depth for the maximum flow rate.
이병서(Byoung Seo Lee),송귀은(Gwi-Eun Song),이준식(Joon Sik Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
A computational fluid mechanics study is performed on valveless diffuser type micropumps for the purpose of designing the micropumps efficiently and making the mechanism clearly understood. The program developed is validated through the comparison of the pressure losses in conic flows. The steady flow analysis is adapted to some diffuser elements and a micropump to present their flow characteristics and efficiencies. The diffuser elements show maximum efficiency of 1.2 at 20 ml/min. The flow structure observed by the steady analysis is coincident with one of various structures that can be observed in visualization of chamber flows.
이병서(Byoung Seo Lee),이주명(Ju Myoung Lee),이준식(Joon Sik Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
A computer program for unstructured grid system is developed, which can describe unsteady fluid flow and heat transfer by the fractional step method and SIMPLE method. The governing equations are discretised based upon the finite concept method, a kind of finite volume method. The validity of the program is established in comparison with the benchmark solutions, which shows good agreements with both two methods. The present study reports difference in computational time depending on two different methods and flow types.
이병서(Byoung Seo Lee),이준식(Joon Sik Lee),유정열(Jung Yul Yoo) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
It is well known that organized vortex rotations swirl and tumble greatly affect the mixing, the<br/> combustion and heat transfer processes in engine cylinder. We have developed 3 dimensional numerical<br/> simulation codes whose predictions make good agreement with the experimental data. Large eddy<br/> simulation based on Smagorinsky subgrid scale model was adopted to describe the turbulence of<br/> in-cylinder flows. The tumble motions generated by different inclination angles between valve-port and<br/> cylinder head have been calculated. The results show that the angles between direction of induced flow<br/> and cylinder walls which the flow collides with play a great role in the formation and generation of<br/> tumble motions. Therefore, it is inferred that seat angle and inclination angle are important factors of<br/> engine design. In addition, the numerical results of different engine speed -1000 rpm and 3000 rpm are<br/> very similar in the flow structure.
객체지향 기법을 이용한 전자연동 소프트웨어의 설계에 관한 연구
이재호(Lee Jae Ho),이병일(Lee Byoung Il),박영수(Park Yong Su),이재훈(Lee Jae Hoon),이기서(Lee Key Seo) 한국철도학회 2000 한국철도학회 학술발표대회논문집 Vol.- No.-
Interlocking software used in the electronic interlocking has been implemented through the structured approach until now. But there was the demerit that interlocking software has some problem in the standardization and the maintenance because of the limit in structured approach. Object-Oriented method overcoming this demerit was specified in the design step and the analysis step. There were object model, dynamic model and functional model in the analysis step and there were also two steps which were system design and object design in the design step. In this paper, Interlocking software was designed using Object-Oriented method to improve the standardization and the maintenance of the electronic interlocking. The electronic interlocking was analyzed with object modeling, dynamic modeling and functional modeling.