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개도율에 따른 가스파이프라인용 볼 밸브 후류유동의 수치평가
김철규,이상문,장춘만,KIM, CHUL-KYU,LEE, SANG-MOON,JANG, CHOON-MAN 한국수소및신에너지학회 2018 한국수소 및 신에너지학회논문집 Vol.29 No.4
Ball valve has been widely used in the field of high-pressure gas pipeline as an important component because of its low flow resistance and good leakage performance. The present paper focuses on the flow nature at the downstream of the ball valve used for gas pipelines according to valve opening rates. Steady 3-D RANS equations, SC/Tetra, have been introduced to analyze the flow characteristics inside the ball valve. Numerical boundary conditions at the inlet and outlet of the valve system are imposed by mass flow-rate and pressure, respectively. Velocity distributions obtained by numerical simulation are compared with respect to the valve opening rates of 30, 50, and 70%. Cavity distributions, asymmetry flow velocity and the flow stabilization point at each opening rate are also compared. When the valve opening rates are 30 and 50%, the flow stabilization requires the sufficient length of 10D or more due to the influence of the recirculation flow at the downstream of the valve.
김철규,전우평,박진일,김동주,최해천,Kim, Chul-Kyu,Jeon, Woo-Pyung,Park, Jin-Il,Kim, Dong-Joo,Choi, Haecheon 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.9
In this study, the modification of turbulent boundary layer flow by local wall vibration is investigated. The wall is locally vibrated using a wall deformation actuator, which moves up and down at the frequencies of 100Hz and 50Hz. Simultaneous measurements of the streamwise velocities in the spanwise direction are performed at several wall-normal and streamwise locations using an in-house multi-channel hot wire anemometer and a spanwise hot-wire-probe rake. The mean velocity is reduced in most places due to the wall vibration and its reduced amount becomes small as flow goes downstream. Interestingly, the mean velocity is found to increase very near the wall and near the actuator. This is due to the motion induced by the streamwise vortices which are generated by the downward motion of the actuator. In case of the streamwise velocity fluctuations, their magnitude increases as compared to the unperturbed turbulent boundary layer, and the increased amount becomes small as the flow moves downstream. The modified flow field at the forcing frequency of 50Hz is not much different from that of 100Hz, except the reduced amount of modification.
The Roles of Questions in English and Korean Science Popularizations
Chul-Kyu Kim(김철규) 담화·인지언어학회 2007 담화와 인지 Vol.14 No.1
Writers use various linguistic devices to construct dialogic interaction between the writer and the reader explicitly in text to enhance the reader's involvement in text. This article, among the various devices, focuses on questions in order to reveal culturally characteristic features between English and Korean science popularizations in newspapers. By using a corpus analysis software for identifying the number of questions in the 356 texts and through setting up analytical categories for describing the genre-specific functions of questions, the analysis reveals that the genre in the two cultures is basically for diffusing scientific knowledge and information to the reader. However, the results also show quantitative and qualitative differences in the two corpora; the English writers employ more questions than the Koreans, and the ways in which questions are used are also different. The English writers tend to use questions to introduce wide-ranging discussions of new scientific knowledge to the reader, whereas the Koreans are likely to utilize them to educate the reader with already proved scientific knowledge. These differences are also reflected in the ways in which the writer aligns his/her persona and the reader's in terms of knowledge-based authority.
대공간 건축물의 안정방식에 따른 형태적 특성에 관한 연구
김철규(Kim Chul-Kyu),조성현(Cho Sung-Hyun) 대한건축학회 2009 대한건축학회논문집 Vol.25 No.3
The purpose of this study is to examine the relationship between the structural system used in modern architecture and the form and spatial composition of the buildings. The principle for the stabilization of structures is closely related to the architectural form. That is, in order to stabilize a building, a special type of structural system is required and consequently shows up with consistent characteristics in the architectural form. Structural systems of modern architecture can be classified into skeletal structure, trusses structure, and space structure according to the structural characteristics. Space structure can be divided into compressible space structure and tensile space structure. Spatial building has formal properties according to the stabilization method of vertical load support elements. Master column, buttress and catenary cable enable the fluent flow of load by combining with mechanical efficiency and are able to deal with the generated stress efficiently. The architectural cases for each type of structure are classified into the form-construction type and the plane-composition type in the aspect of architectural effect.