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전산유체역학을 활용한 자주도하장비 문교 상태의 저항 및 자항 성능 평가
이인수(I. Lee),서정화(J. Seo),석우찬(W. Seok),유재훈(J. Yoo),이강일(K.I. Lee),김도헌(D.H. Kim),이남훈(N. Lee),이성오(S.O. Lee),이신형(S.H. Lee) 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.4
In this study, numerical simulations were conducted for resistance and self-propulsion performance for an amphibious rig in ferry mode. They were performed under conditions of h/T=4.5, 2.0 and head angles of both 180 and 90 degrees using SNUFOAM, based on open source CFD toolkit OpenFOAM. A double body method was adopted for free surface flow. Thrust was modeled with a body force method in self propulsion tests. The results of resistance tests showed drag forces according to the depth and head angle conditions and presented differences in the drag forces. In order to investigate the differences, the pressure, velocity, and vorticity distribution near the amphibious rig were identified. From self propulsion tests results, the thrusts and powers at the self propulsion point were estimated and compared with the thrust diagram to confirm the self propulsion performance.
높은 받음각 영역에서 plunge 운동을 하는 강체 평판의 공력 성능
이남훈(N. Lee),안계현(K. Ahn),이승수(S. Lee),조해성(H. Cho),신상준(S.-J. Shin) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.3
In this paper, the aerodynamic performance of a rigid plunging plate at high angles of attack is presented. The forces acting on the plate at a post-stall angle of attack of 15 degrees with the amplitude of 15% of the chord are computed, and compared with the experimental results. For the numerical simulation, a three-dimensional preconditioned Navier-Stokes solver is adopted. When compared to the experimental results, the present method capture not only the trend of the averaged force coefficients but also the characteristics of the flow fields.
이남훈,성원경,김소연,박성하,강원남,Lee, N.H.,Seong, W.K.,Ranot, Mahipal,Kim, So-Yeon,Park, Sung-Ha,Kang, W.N. 한국초전도학회 2009 Progress in superconductivity Vol.11 No.1
We investigated the effects of the irradiation of light-ions on the superconducting $MgB_2$ thin films fabricated by using HPCVD. Deuterium and helium ions were irradiated on $MgB_2$ thin films by various doses, from $1{\times}10^{10}cm^{-2}\;to\;8{\times}10^{15}cm^{-2}$. During these experiments some reasonable results and unpredictable results have been obtained. The reasonable results are that the peak of the reduced maximum pinning force shifts by increasing the pinning sites in $MgB_2$ films and the slightly change of critical current density of films. We obtained some unusual results, which are the increasing of the transition temperature and the change of residual resistance ratio. Among the data of deuterium and helium ion irradiation experiments, the results of helium ion irradiation have most notable points so we will discuss mainly about helium irradiation experiments.
선진 자동차 재제조 산업 분석을 통한 국내 산업에의 시사점 : 교류발전기와 시동전동기를 중심으로
김형주(H. J. Kim),Guenther Seliger,정남훈(N. H. Chung),이한홍(H.H. Lee) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
Post industrial technologies have improved human standard of living, however, a host of negative environmental consequences from the unlimited industrial appetite have posed serious global challenges. Remanufacturing is an industrial manufacturing process that is to restore old products to perform like a new and to save energy, natural resources, landfill space and to reduce air pollution by less re-smelting. By extending product life cycle, remanufacturing gives us enormous opportunities for sustainable development of our society. This paper introduces current state of the art and future perspective in the field of automotive remanufacturing focusing on alternator and start motor. The results could be used as a basic information for further remanufacturing applications in Korea.
비정상/비압축성 유동해석을 위한 가상압축성 기법이 적용된 이중시간적분법의 수렴특성 연구
이형로(H.R. Lee),이남훈(N.H. Lee),이승수(S. Lee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
In this study, parametric studies on the artificial compressibility coefficient are performed to investigate convergence characteristics of the dual time stepping method. Convergence characteristics is evaluated by the residual of the continuity equation for various values of the artificial compressibility coefficient. For numerical simulations, Roes approximate Riemann solver in conjunction with a cell centered finite volume method is used. Numerical simulations are performed for unsteady problems with stationary and moving grids. The speed of convergence are compared in terms of the artificial compressibility coefficient. From the results, a proper range of the artificial compressibility coefficient to obtain a high speed of convergence are confirmed.
PLD법을 이용한 다양한 온도에서의 $FeSe_x$ 초전도 박막 성장
정순길,이남훈,강원남,황태종,김동호,Jung, Soon-Gil,Lee, N.H.,Kang, W.N.,Hwang, Tae-Jong,Kim, D.H. 한국초전도학회 2011 Progress in superconductivity Vol.13 No.2
We have fabricated $FeSe_x$ superconducting thin films at much different substrate temperatures of 430 and $610^{\circ}C$ on $Al_2O_3$(0001) substrates by using a pulsed laser deposition (PLD) technique. Superconducting transitions for both films were shown around 10 K, but their transition width and growth directions of grains were different. We found that superconducting tetragonal FeSe phases and non-superconducting hexagonal FeSe phases were coexisted in the sample grown at the low temperature of $430^{\circ}C$, whereas the hexagonal FeSe phase was decreased with increasing fabrication temperatures.