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이강남(K. N. Lee),정광효(K. H. Jung),채영준(Y. J. Chae),박일룡(I. R. Park),서성부(S. B. Suh) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.2
In this study, the green water phenomena on rectangular shaped structure is numerically simulated by STAR-CCM+ to investigate the flow pattern including the velocity profiles in bubbly water flow. 5 phases of the formation of green water in front of and over the rectangular shaped structure is simulated at the design condition which is scaled down by 1:125 from FPSO operating in GOM. All numerical results are compared with the experimental results performed in a two dimensional wave flume. The water deformation due to the green water are obtained by the high speed CCD camera with employing the shadow graphy technique, which is allowed to take the bubbly water flow into images. A series of image taken by shadow graphy technique is analyzed with MQD method to calculate the velocity in bubbly water flow.
Nitrocarburising 처리된 탄소강의 내식특성에 미치는 Post Oxidation 효과
김영희,정광효 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.1
The effect of post oxidation, water-quenched after holding in air for 5∼420 seconds or cooling or furnace cooling, on corrosion resistance and phase formation characteristics of the surface layer of SM20C and SM45C carbon steels after gas nirtrocarbursing in the NH₃-5%CO₂-N₂gas atmosphere at 580℃ for 3hours is studied. The compound layers of two steels consist of ε-Fe_(2-3)N, γ'-Fe₄N and Fe₃O₄, phases, however, the quantity of γ'-Fe₄N phase increases for the furnace cooled specimen compared to that of air cooling specimen. With increasing NH₃content in the gas mixture and also increasing the keeping time in the air after gas nitrocarburising, the ε-Fe_(2-3)N phase of compound layer increases, while the decreased current density recognizing the improvement of corrosion resistance are shown. the passive current density of SM45C steel is lower than that of SM20C steel at the same nitrocarburising conditions.