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선형 격자 형성 방정식을 이용한 직교 격자 형성에 관한 연구
이상욱(S. W. Lee),권장혁(J. H. Kwon),권오준(O. J. Kwon) 한국전산유체공학회 2000 한국전산유체공학회지 Vol.5 No.1
A method of two and three dimensional orthogonal grid generation with control of spacing by using the covariant Laplace equation is presented. An important feature of the methodology is its ability to control effectively the grid spacing especially near the boundaries still maintaining good orthogonality in whole field.<br/> The method is based on the concept of decomposition of the global transformation into consecutive transformation of an approximate conformal mapping and an auxiliary orthogonal mapping to have linear and uncoupled equations. Control of cell spacing is based on the concept of reference arc length, and orthogonal correction is performed in the auxiliary domain.<br/> It is concluded that the methodology can successfully generate well controlled orthogonal grids around bodies of 2 and 3 dimensional configurations.
이상욱(S.W. Lee) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.3
In this paper, the applicability of OpenFOAM in automotive air flow analysis is studied. Among the various incompressible flow analysis programs provided, simpleFoam is utilized for both the external and internal air flow analysis(External air flow: Simple vehicle shape and realistic vehicle model, Internal air flow: ventilation duct and cabin room). For the validation of external flow, aerodynamic drag coefficient and surface pressure distributions are investigated and compared with the values from wind tunnel test. The resultant of them turns out to be similar with those of wind tunnel test. Especially, aerodynamic drag coefficient is within 1% error for realistic vehicle model, DrivAer. For the validation of internal flow, results are compared with those of commercial CFD program, FLUENT. Correlation between two CFD programs is evaluated by comparing total pressure drop through ventilation duct and it is shown that 92% of coincidence exists between two programs.
비드가 있는 직사각컵 딥드로잉 공정의 3차원 유한 요소 해석의 비교 연구
양동열(D.Y.Yang),이상욱(S.W.Lee),윤정환(J.W.Yoon),이동우(D.W.Lee) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
In this work, three kinds of analysis methods; i.e., elastoplastic shell/implicit method, elastoplastic shell/explicit method and rigid-plastic continuum/implicit method, are compared and discussed for analyzing a rectangular 'cup deep drawing with beads under the same computational circumstances. They are also compared with the experimental results to clarify the differences of formulation. From the comparisons, their merits and demerits have been discussed.
Aerospatiale A-airfoil 주위 천이-난류 유동의 대와류모사기법 적용에서의 격자영향 연구
최지원(J.W. Choi),장경식(K.S. Chang),이상욱(S.W. Lee),김건홍(G.H. Kim) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.2
In this study, the grid effect based on WALE LES model is analyzed using the open source OpenFOAM. The numerical analysis is performed on the flow around the Aerospatiale A-airfoil of high Reynolds number, Rec=2.1×10<SUP>6</SUP>. Four grid systems with different grid resolutions in the streamwise and spanwise directions are considered to be compared with reference data. Mean velocity profiles and pressure distributions are presented according to the different grid systems and time averaged drag and lift coefficients are compared. Reynolds stress profiles also are presented. As the grid resolution increases, the prediction of transitional flow features and the fluctuations in turbulent flow are better. However, it is confirmed that higher gird resolution is required for better quantitative agreement with experimental data.
이상욱(Lee S.W.) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.8
본 연구는 미시 수준의 기업 자료를 이용하여 정부소유 은행과 거래 기업의 규모에 대해 다양한 실증분석을 실시하였 다. 기업과 정부소유 은행 관계는 정부소유은행과의 최다대출관계 여부, 정부소유은행의 대출비중 등을 이용하였다. 또한 정부소유 은행관계가 기업 규모에 미치는 영향에 대한 내생성 문제를 통제하기 위해 시차변수, 도구변수를 이용한 이단계 최소자승 모형 등을 이용하였다. 또한 분석결과에 미칠 수 있는 요인을 통제하기 위해 다양한 관점에서의 통제변수를 이용하 였다. 분석 결과에 따르면 정부소유 은행과 주거래 관계에 있거나 정부소유 은행으로부터 많은 대출을 의존할수록 거래기업 의 규모가 작은 것으로 나타났다. 본 연구 결과를 통해 정부소유 은행과 주된 거래관계에 있거나 정부소유 은행들로부터 상대적으로 많은 대출을 의존하는 기업들의 규모는 상대적으로 작은 것으로 추정할 수 있다. 즉 정부소유 은행과 관계가 긴밀할수록 기업의 규모가 작은 기업들이라고 추정할 수 있다. 본 연구는 은행의 정부소유 여부 등 은행 소유 지배구조, 은행 과 기업의 관계 등에 새로운 시사점을 제공하고 있다. 또한 본 연구는 은행의 민영화 진행 과정에서 정부소유 은행의 긍정적 기능을 살펴 보았다는 점에서도 시사점이 있다. This study examined the impact of Government-ownership of banks on the firm size using South Korean data. The impact of Government ownership of banks as both the largest lender of government banks and the bank loan dependency of firms on government-ownership bank were measured. Empirical models considering endogenous problems and various effects of firm size were developed. All results in this paper showed that government-ownership of the main banks might have a relationship with the smaller firms. In addition, the bank loan dependency of firms on government-ownership banks might have effects on the firm size. A higher loan dependency of firms on government-owned banks resulted in smaller firms. This study used micro firm level data to analyze, from several perspectives, the relationship between government-owned banks and firm size. The existing studies go as far as inferring the effects of government-owned banks showing theoretical evidence, performing surveys, or using international comparison data. This study is differentiated from existing studies in that it analyzed in a direct manner the effects of the government-owned banks on both the firm size. This study provides insights into the privatization of government-owned banks.