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LES를 이용한 초음속 충돌제트의 피드백 메커니즘에 대한 수치해석 연구
오세홍,최대경,김원태,장윤석,최청열,Oh, Se-Hong,Choi, Dae Kyung,Kim, Won Tae,Chang, Yoon-Suk,Choi, Choengryul 한국압력기기공학회 2017 한국압력기기공학회 논문집 Vol.13 No.2
Steam jets ejected from a rupture zone of high energy pipes may cause damage to adjacent structures. This event could lead to more serious accidents in nuclear power plants. Therefore, to prevent serious accidents, high energy pipes of nuclear power plants are designed according to the ANSI / ANS 58.2 technical standard. However, the US Nuclear Regulatory Commission (USNRC) has recently pointed out non-conservatism in existing high energy pipe fracture evaluation methods, and required the assessment of the unsteady load of the jet caused by a potential feedback mechanism as well as the impact range of steam jet, the jet impact loads and the blast wave effects at the initial breakage stage. The potential feedback mechanism refers to a phenomenon in which a vortex formed by impingement jets amplifies vortex itself and induces jet vibration in a shear layer. In this study, CFD methodology using the LES turbulence model is established and numerical analysis is carried out to evaluate the dynamic behavior of impingement jets and the potential feedback mechanism during jet impingement. Obtained results have been compared with an empirical correlation and experiment.
전자기 저항을 이용한 열공압형 마이크로 펌프에서 통전유체의 유동 및 펌핑 특성에 관한 연구
오세홍(Se Hong Oh),용정권(Jung Kwon Yong),김창녕(Chang Nyung Kim) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.1
An analysis has been conducted of the flow characteristics and pumping performance of a thermopneumatic micropump with electrically conducting fluid. In the present study, considered is a thermopneumatic micropump for electrically conducting fluids with electromagnetic resistance alternately exerted at the inlet and outlet by alternately applied magnetic fields. A model of Prescribed Deformation is used for the motion of the membrane. Here, the pumping performance of the micropump and flow characteristics of the electrically conducting fluid are investigated in the range of Hartmann number less than 30. The current numerical study shows that the net flow rate through the micropump is almost proportional to the strength of the applied magnetic field.
오세홍(Se Hong Oh),황경모(Kyeong Mo Hwang),서혁기(Hyuk Ki Seo),윤훈(Hun Yun),손성만(Sung Man Son),최청열(Choeng Ryul Choi) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Liquid droplet impingement erosion (LDIE) is caused by continued exposure to impact by liquid droplets on solid surface. LDIE could be regarded as one of the major causes of unexpected troubles occasionally occurred in the inner bent pipe surface. Therefore, evaluating LDIE is an important topic of the thermal hydraulics and structural integrity in aging and life extension for nuclear power plants. In this study, first, several thinning rate correlations are reviewed and compared. And then, LDIE phenomenon in steam piping systems containing liquid droplets is simulated by using fluidstructure interaction (FSI) approach. Wall thinning phenomenon due to LDIE is presented as wall deformation in FSI approach. From the simulation, wall thinning depth is calculated. As wall thinning progressed, flow direction, droplet trajectory, and impact angle change with exposure time due to shape deformation of target wall. Therefore, it is important to consider the deformation of wall shape for accuracy.
발전소 배관계통의 유동유발진동 현상에 대한 수치해석 연구
오세홍(Se-Hong Oh),한진(Jin Han),홍화선(Hwa-Sun Hong),이종일(Jong-Il Lee),손성만(Sung-Man Son),최청열(Choengryul Choi) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
Numerical analysis has been conducted in order to investigate the cause of piping vibration problem in thermal power plants. Piping vibration due to instability of the fluid flow is referred to flow-induced vibration(FIV), which could inhibit the structural integrity of piping system and its supporting structures. In this work, large eddy simulation(LES) and frequency analysis have been performed to evaluate the vibrational characteristics of the pipeline behind centrifugal pump. Although flow-induced vibration can be caused by a variety of reasons, present study focused on vibration phenomena only due to unstable fluid flow such as turbulence and vortex shedding. Especially, the effects of opening ratio of the discharge valve on the vibrational characteristics was mainly evaluated.
전자기 저항을 이용한 열공압형 마이크로 펌프의 유동특성 및 펌핑성능에 관한 수치해석적 연구
오세홍(Se Hong Oh),최청렬(Chung Ryul Choi),김창녕(Chang Nyung Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
A numerical analysis has been conducted for the flow characteristics and pumping performance of a thermo-pneumatic micropump with electrically conducting fluid. In the present study, considered is a thermo-pneumatic micropump for electrically conducting fluids with electromagnetic resistance alternately exerted at the inlet and outlet by alternately applied magnetic fields. A model of Prescribed Deformation is used for the motion of the membrane. Here, the pumping performance of the micropump and flow characteristics of the working fluid are investigated in the range of magnetic field intensity. The present numerical study shows that the net flow rate through the micropump is almost proportional to the strength of the applied magnetic field.
최청열,오세홍,최대경,김원태,장윤석,김승현,Choi, Choengryul,Oh, Se-Hong,Choi, Dae Kyung,Kim, Won Tae,Chang, Yoon-Suk,Kim, Seung Hyun 한국압력기기공학회 2016 한국압력기기공학회 논문집 Vol.12 No.2
Since, in case of high energy piping, steam jets ejected from the rupture zone may cause damage to nearby structure, it is necessary to design it into consideration of nuclear power plant design. For the existing nuclear power plants, the ANSI / ANS 58.2 technical standard for high-energy pipe rupture was used. However, the US Nuclear Regulatory Commission (USNRC) and academia recently have pointed out the non-conservativeness of existing high energy pipe fracture evaluation methods. Therefore, it is necessary to develop a highly reliable evaluation methodology to evaluate the behavior of steam jet ejected during high energy pipe rupture and the effect of steam jet on peripheral devices and structures. In this study, we develop a method for analyzing the impact load of a jet by high energy pipe rupture, and plan to carry out an experiment to verify the evaluation methodology. In this paper, the basic data required for the design of the jet impact load experiment equipment under construction, 1) the load change according to the jet distance, 2) the load change according to the jet collision angle, 3) the load variation according to structure diameter, and 4) the load variation depending on the jet impact position, are numerically obtained using the developed steam jet analysis technique.