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원형단면 노즐의 급확대 축소부를 통한 유동손실에 대한 연구
고영하 한국마린엔지니어링학회 2000 한국마린엔지니어링학회지 Vol.24 No.6
To obtain an exact flow loss in piping systems is very important in the face of efficiency anticipation and work control of plant. The object of this study is to get the flow loss through the experiment for sudden expansion and contraction part of circular pipe nozzle. The experiment in this study is performed after getting the flow loss factor for sudden expansion and contraction through preliminary experiments. It is confirmed that the results of this study agreed with the approximated equation of Ikeda and Matsuo. It is proved that flow loss factor ${\zeta}_3$for sudden expansion and contraction part of circular pipe is dependent on $L/D_1$in these experimental conditions.
정4각덕트의 입구영역에서 난류정상유동의 실험해와 수치해의 비교에 관한 연구
고영하,박길문,봉태근 한국마린엔지니어링학회 1997 한국마린엔지니어링학회지 Vol.21 No.3
The flow characteristics of developing turbulent steady flow are investigated numerically and experimentally in the entrance region of a square duct ($40 mm{\times}40 mm$ and 4, 000 mm). The numerical anaysis are incorporated by finite- volume discretization with staggered grid system and SIMPLE algorithm. The numerical solution are compared with experimental results of mean velocity profiles, turbulence intensity and entrance length. For turbulent steady flow, the turbulent components in the velocity waveforms increase as the dimensionless transverse position approaches the wall. Thrbulence intensity increases as the dimensionless transverse position increases from the center to the wall of the duct for the developing turbulent steady flows. The entrance length of the turbulent steady flow is about 40 times as large as the hydraulic diameter under the present experimental condition.
Development and Verification of Fatigue Testing Device for Rail Fastening Clamps
고영하,Xiao-Jun Fang,박연철,허종완,심형보 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.3
The rail fastening clamp (or clip) is a crucial part of the rail fastening system that links the rail to the sleeper and transmits the trainload to the substructure. Due to the large tensile stress that occurs during initial fastening and the stress fluctuation that occurs during train operation, this clamp is structured to be vulnerable to fatigue. Furthermore, if concurrent damage occurs at the site, it can result in the train’s derailment, therefore careful control is important to prevent it. Recently, fatigue-induced damage in clamps have been reported during train operations on railway lines, however, research into this is lacking. In this study, the existing fatigue test research cases for the rail fastening system clamps that are extensively used at home and overseas were investigated. A novel fatigue testing device that can replace the present fatigue testing method was designed based on this. A fatigue test was conducted on a tension clamp (SKL15) and the experimental equipment’s appropriateness was assessed through data analysis to confirm the developed experimental equipment.
고영하 한국마린엔지니어링학회 2003 한국마린엔지니어링학회지 Vol.27 No.7
The purpose of this study was to measure the surface tension of hard water through electro-magnetic field for investigating the effect of electro-magnetic water treatment. The maximum reduction of surface tension was 8% comparing to the no treatment case. When the flow velocity through the permanent magnetic device (PMD) was 6.3 m/s, sample of hard water had the minimum surface tension.
정4각덕트의 입구영역에서 난류 비정상유동에 대한 이론과 실험적 연구
고영하 한국마린엔지니어링학회 1998 한국마린엔지니어링학회지 Vol.22 No.5
Turbulent unsteady flows in the entrance region of a square duct are investigated with a hot-wire anemometer system. The velocity waveforms the mean and turbulence components of the axial velocity and the entrance length are obtained as a major characteristics of the developing turbulent unsteady flows. An inviscid flow theory is presented to describe the developing axial mean velocity profiles. A good agreement is seen between the measured and theoretically predicted values. The propagation of turbulence generated near the entrance of the square duct is satisfactorily approximated by an empirical correlation of the propagation of turbulence proposed so far. The local turbulence intensi-ty is found to be a little smaller in the accelerating phase than in the decelerating phase. The entrance length is about 60 times as large the hydraulic diameter.