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유럽 측면충돌 성능향상을 위한 차체 측면구조 대책과 해석
홍성오(S.O.HONG),홍석길(S.G.HONG),이익중(I.J.LEE) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
Since the European Experimental Vehicle Committee(EEVC) has proposed a new side impact procedure, car designers should consider improving crashworthness not only for the NHTSA side impact but also for the proposed EEVE side impact.<br/> This paper presents a computer simulation of passenger car structure and occupant in the European side impact. The simulation is done by LS-DYNA3D on Cray T-94 to calculate the deformation and movement of the structure and dummy injury criteria. The purpose of the analysis is to find ways of reducing the door and b-pillar velocities and deformations, as these data are related to dummy injury criteria. From the result we have proposed the effective structure modified for the European side impact.<br/>
연마공정에서 MR 유체의 트라이볼로지적 성질에 대한 연구
이성오(S. O. Lee),장경인(K. I. Jang),민병권(B.-K. Min),이상조(S. J. Lee),석종원(J. Seok) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
Tribological properties of a Magneto-Rheological(MR) fluid in a polishing process are studied. For this polishing process, abrasive wear model is proposed as a function of shear force, normal force and actual mean velocity of MR particles at workpiece surface. Experimental conditions are changed by varying the gap distance between workpiece and tool and the rotational speed of tool. From the experimental results, a modified Stribeck curve is obtained, and the friction coefficient turns out to have linear relationship with a modified Sommerfeld number. The validity of the wear model is supported by additional experiments performed for measuring material removal rates.
Buongiorno의 비균질 모델을 사용한 나노유체의 층류 자연대류 해석
최석기(S.K. Choi),김성오(S.O. Kim),이태호(T.H. Lee) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.4
A numerical study of a laminar natural convection of the CuO-water nanofluid in a square cavity using the Buongiornos nonhomogeneous model is presented. All the governing equations including the volume fraction equation are discretized on a cell-centered, non-uniform grid employing the finite-volume method with a primitive variable formulation. Calculations are performed over a range of Rayleigh numbers and volume fractions of the nanopartile. From the computed results, it is shown that both the homogeneous and nonhomogeneous models predict the deterioration of the natural convection heat transfer well with an increase of the volume fraction of nanoparticle at the same Rayleigh number, which was observed in the previous experimental studies. It is also shown that the differences in the computed results of the average Nusselt number at the wall between the homogeneous and nonhomogeneous models are very small, and this indicates that the slip mechanism of the Brown diffusion and thermophoresis effects are negligible in the laminar natural convection of the nanofluid. The degradation of the heat transfer with an increase of the volume fraction of the nanoparticle in the natural convection of nanofluid is due to the increase of the viscosity and the decrease of the thermal expansion coefficient and the specific heat. It is clarified in the present study that the previous controversies between the numerical and experimental studies are owing to the different definitions of the Nusselt number.
Buongiorno의 비균질 모델을 사용한 나노유체의 층류 자연대류 해석
최석기(S.K. Choi),김성오(S.O. Kim),이태호(T.H. Lee) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.4
A numerical study of a laminar natural convection of the CuO-water nanofluid in a square cavity using the Buongiorno"s nonhomogeneous model is presented. All the governing equations including the volume fraction equation are discretized on a cell-centered, non-uniform grid employing the finite-volume method with a primitive variable formulation. Calculations are performed over a range of Rayleigh numbers and volume fractions of the nanopartile. From the computed results, it is shown that both the homogeneous and nonhomogeneous models predict the deterioration of the natural convection heat transfer well with an increase of the volume fraction of nanoparticle at the same Rayleigh number, which was observed in the previous experimental studies. It is also shown that the differences in the computed results of the average Nusselt number at the wall between the homogeneous and nonhomogeneous models are very small, and this indicates that the slip mechanism of the Brown diffusion and thermophoresis effects are negligible in the laminar natural convection of the nanofluid. The degradation of the heat transfer with an increase of the volume fraction of the nanoparticle in the natural convection of nanofluid is due to the increase of the viscosity and the decrease of the thermal expansion coefficient and the specific heat. It is clarified in the present study that the previous controversies between the numerical and experimental studies are owing to the different definitions of the Nusselt number.