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적합직교분해를 이용한 2차원 실린더 후류 유동장 분석 및 재구성
이희남,김기희,Rhee, Hui-Nam,Kim, Gi-Hee 한국군사과학기술학회 2010 한국군사과학기술학회지 Vol.13 No.1
Proper Orthogonal Decomposition (POD) is applied to the analysis of 2-dimensional cylinder wake flow. Time histories of flow variables were obtained by the incompressible CFD analysis. By using the method of snapshots the correlation matrix was constructed, and then eigenvalues, POD modes and time coefficients were calculated. Finally the flow field was reconstructed by using a few of the lower POD modes, and compared to the original ones.
이희남(Rhee, Hui-Nam),김태성(Kim, Tae-Sung),전완호(Jeon, Wan-Ho),김현구(Kim, Hyun-Goo) 한국태양에너지학회 2013 한국태양에너지학회 논문집 Vol.33 No.1
It is difficult to avoid measurement errors caused by the shading effect of the meteorological tower, which is used for wind resource assessment according to the IEC Standard. This paper presents a validation of the computational flow analysis results by comparing the results with the wind tunnel experiment conducted for Reynolds numbers in the104 to105 range, for the preparation of a database for use in an automatic method of correcting met-tower shading errors. A three-dimensional simulation employing the MP (Modified Production) k-ԑ turbulence model predicted a wind speed deficit in the wake region according to minimum wind speed ratio, within an MAE (Mean Absolute Error) of 2.4%.
울진 원자력발전소 5,6 호기용 공기정화기에 대한 내진검증
김진영,이희남,이준근,Kim, Jin-Young,Rhee, Hui-Nam,Lee, Joon-Keun 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.7
Seismic qualification of the Air Cleaning Units for nuclear power plant Ulchin 5&6 has been performed with the guideline of ASME Section III and IEEE 344 code. By using the structural and geometrical similarity analysis, the three models to be analyzed are condensed into a single model and, at the same time, the excitation forces and other operating loads for each model are encompassed with respect to different loading conditions. As the fundamental frequencies of the structure are found to be less than 33Hz, which is the upper frequency limit of the seismic load, response spectrum analysis using ANSYS is performed in order to combine the modal stresses within the frequency limit. In order to confirm the structural and electric stability of the major components, modal analysis theory is adopted to derive the required response spectrum at the component locations. As the all combined stresses obtained from the above procedures are less than allowable stresses and no mechanical or electrical failures are found from the seismic testing, the authors confirm the safety of the nuclear equipments Air Cleaning Units studied in this paper.
박치용(Chi-Yong Park),김태룡(Tae-Ryong Kim),이희남(Hui-nam Rhee),유기완(Ki-Wahn Ryu) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
A in-house computer program has been developed recently which is able to perform modal analysis of tubes of a heat exchanger in a very efficient way. This program can automatically calculate mode shapes and natural frequencies for selected tube, and its results may be used on the evaluation of flow induced vibration for heat exchanger tubes. In this study, reliability assessment of the developed in-house program was carried out by comparing modal frequencies with a commercial program and by using the modal assurance criteria, which is a methodology for estimation of quantitative similarity between corresponding mode shapes. Based on assessment results, a previously developed modal analysis computer program could be used in the evaluation of dynamic integration and wear damage due to flow induced vibration.
물-공기 횡류시 U 자형 튜브 다발에서의 유체탄성불안정
주인철(In-Cheol Chu),정흥준(Heung June Chung),이창희(Chang Hee Lee),윤영중(Young Jung Yun),정한섭(Han-Sub Chung),변형현(Hyung Hyun Byun),김무용(Moo Yong Kim),문효익(Hyo Ik Moon),이희남(Hui Nam Rhee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In the present study, a series of experiments have been performed to investigate a fluid-elastic instability of an U-tube bundle in air-water two-phase cross-flow. A total of 39 prototypic U-bend tubes are arranged in a rotated square array with a p/d of 1.633, which is identical to U-bend tube bundle of OPR1000 steam generators. The present experimental facility has 2-span U-tubes in contrast to 9-span U-tubes of OPR1000 steam generators. However, modal analysis shows that the major vibration mode and corresponding natural frequencies are almost same to the full 9-span U-tubes. A total of 12 3-axis acceleromters are installed inside U-tubes to monitor a precise vibration motions. The following parameters were obtained throughout a series of experiments: tube vibration responses and critical velocity for fluid-elastic instability, two-phase damping ratio, hydrodynamic mass. Finally, the instability factor (K) of Connors’ relation was evaluated based on the above measured parameters.