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해수배관 내부 에폭시 코팅재의 캐비테이션 및 침지 열화에 따른 압입인장특성
정민재 ( M. J. Jung ),김수현 ( S. H. Kim ),전종모 ( J. M. Jeon ),김영식 ( Y. S. Kim ),김영천 ( Y. C. Kim ) 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.6
Seawater has been used to cool devices in nuclear power plants. However, the pipes used to transport seawater are vulnerable to corrosion; hence, the inner side of pipelines is coated with an epoxy layer as prevention. Upon coating damage, the pipe becomes exposed, and corrosion progresses. The major cause is widely known as cavitation corrosion, causing the degradation of mechanical properties. In this study, corroded specimens were prepared using cavitation and immersion methods to clarify the degradation trend of mechanical properties with corrosion. Three different types of epoxy coatings were used, and accelerated cavitation procedures were composed of amplitudes of 15 μm, 50 μm, and 85 μm for 2 h, 4 h, and 6 h. The immersion periods were 3 and 6 weeks. We conducted instrumented indentation tests on all degradation samples to measure mechanical properties. The results showed that higher cavitation amplitudes and longer cavitation or immersion times led to more degradation in the samples, which, in turn, decreased the yield strength. Of the three samples, the C coating had the highest resistance to cavitation and immersion degradation.
피칭운동을 고려한 우주발사체 형상의 천음속 비정상 유동해석
김동현(D.H. Kim),김요한(Y.H. Kim),김동환(D.H. Kim),윤세현(S.H. Yoon),김광수(G.S. Kim),장영순(Y.H. Jang),김수현(S.H. Kim) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.1
In this study, steady and unsteady aerodynamic analyses of a huge rocket configuration have been conducted in a transonic flow region. The launch vehicle structural response are coupled with the transonic flow state transitions at the nose of the payload fairing. Before performing the coupled fluid-structure transonic aeroealstic simulations transonic aerodynamic characteristics are investigated for the pitching motions of the rocket at finite angle-of-attack. An unsteady CFD analysis method with a moving grid technique based on the Reynolds-averaged Navier-Stokes equations with the k-w SST transition turbulence model is applied to accurately predict the transonic loads of the rocket at pitching motion. It is shown that the fluctuating amplitude of the lateral aerodynamic loads imposed on the rocket due to the pitching motion can be significantly increased in the transonic flow region.
피칭운동을 하는 대형 우주발사체 형상의 천음속 비정상 유동해석
김동현(D. H. Kim),김요한(Y. H. Kim),김동환(D. H. Kim),윤세현(S. H. Yoon),김광수(G. S. Kim),장영순(Y. H. Jang),김수현(S. H. Kim) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.11
In this study, steady and unsteady aerodynamic analyses of a huge rocket configuration have been conducted in the transonic flow region. Launch vehicle structural response can couple with transonic flow state transitions at the nose of payload fairing. Before doing fluid-structure coupled transonic aeroealstic simulations for a huge rocket configuration, transonic aerodynamic characteristics are investigated for pitching motions of the rocket with angle-of attack. Unsteady CFD analysis method with moving grid technique based on Reynolds-averaged Navier-Stokes equations with κ-ω SST transition turbulence model is applied to accurately predict the transonic loads of the rocket with pitching motion. It is importantly shown that the fluctuated amplitude of lateral aerodynamic loads imposed on the rocket due to pitching motion can be significantly increased in the transonic region when the rocket has certain angle-of-attack.
S.J. Hong(홍석진),T.T. Tran(트란 탄 도안),D.H. Kim(김동현),Y.S. Kwak(곽영섭),S.H. Kim(김수현) 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.11
Recently, many numerical methods based on potential flow theory have been used to analyze the hydrodynamic effect of a floating body, particularly floating offshore wind turbine. However, conventional potential based methods can not directly and accurately consider the complex viscous interference effects for the motion of multi-structure platform geometry. To accurately account for this effect, it essentially requires additional numerical modification process based on experimental data. This paper deals with unsteady computational fluid dynamic (CFD) analysis of a semi-submersible platform for a floating offshore wind turbine (FOWT) with dynamic motion based on overset grid approach. In this study, a coupled flow and multi-body dynamic analysis has been applied based on the volume of fraction (VOF) approach to investigate the hydrodynamic responses of a typical semi-submersible floater. A mooring system is also considered. It is practically shown that the present results show good correlations with experimental data as it is without any further modification unlike other potential based method.