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부유식 가변 피치형 수직축 풍력발전기의 발전효율에 관한 실험 연구
김재희(Jae-Heui Kim),조효제(Hyo-Jae Jo),황재혁(Jae-Hyuk Hwang),장민석(Min-Suk Jang),이병성(Byeong-Seong Lee) 한국해양공학회 2018 韓國海洋工學會誌 Vol.32 No.3
This paper presents the efficiency of a floating vertical axis wind turbine with variable-pitch. A model was designed to use the lift force and drag force for blades with various pitch angles. The blade"s pitch angle is controlled by the stopper. To validate the efficiency of the wind turbine discussed in this paper, a model test was carried out through a single model efficiency experiment and wave tank experiment. The parameters of the single model efficiency experiment were the wind speed, electronic load, and pitch angle. The wave tank experiment was performed using the most efficient pitch angle from the results of the single model efficiency experiment. According to the results of the wave tank experiment, the surge and pitch motion of a structure slightly affect the efficiency of a wind turbine, but the heave motion has a large effect because the heights of the wind turbine and wind generator are almost the same.
장민석(Min-Suk Jang),조효제(Hyo-Jae Jo),황재혁(Jae-Hyuk Hwang),김재희(Jae-Heui Kim),이병성(Byeong-Seong Lee),박충환(Chung-Hwan Park) 한국해양공학회 2017 韓國海洋工學會誌 Vol.31 No.3
A cylindrical structure has a very long period of heave and pitch motion response in ocean waves. To obtain the dynamic stability of a cylindrical structure, it is necessary to obtain the suitable metacentric height (GM). However, in a structure with sufficient metacentric height, Mathieu instability can occur if the natural frequency of the heave motion is double the natural frequency of the roll and pitch motion. This study carried out numerical calculations and experiments for vertical-axis wind turbines with cylindrical floaters, which had three different centers of gravity. In the regular wave experiment, the divergence of the structure motion without yaw was observed when the natural frequency of the heave motion was double the natural frequency of the roll and pitch motion. In the irregular wave experiment, the motion spectra of the structures with the different centers of gravity were compared, and one was very high when the natural frequency of the heave motion was double the natural frequency of the roll and pitch motion.
부유식 수직축 풍력발전 시스템의 운동특성 및 계류특성에 대한 연구
장민석(Min-Suk Jang),조효제(Hyo-Jae Jo),황재혁(Jae-Hyuk Hwang),김재희(Jae-Heui Kim),김헌우(Hyen-Woo Kim) 한국해양공학회 2017 韓國海洋工學會誌 Vol.31 No.3
This paper presents the results of an experimental study on the motions and mooring characteristics of a floating vertical axis wind turbine system. Based on a comparison of regular wave experiment results, the motions of structures with different types of mooring are almost the same. Based on the tension response results of a regular wave experiment with a catenary mooring system, the mooring lines in front of the structure have a larger tension effect than the back of the structure by the drifted offset of the structure. The dynamic response spectrum of the structure in the irregular wave experiments showed no significant differences in response to differences in the mooring system. As a result of the comparison of the tension response spectra, the mooring lines have a larger value with a drifted offset for the structure, as shown in the previous regular wave experiment. The results of the dynamic response of the structure under irregular wave and wind conditions showed that the heave motion response is influenced by the coupled effect with the mooring lines of the surge and pitch motion due to the drifted offset and steady heeling. In addition, the mooring lines in front of the structure have a very large tension force compared to the mooring lines in back of the structure as a result of the drifted offset of the structure.
String을 이용한 원형실린더 주위의 수평력 감소에 관한 연구
백동일(Dong-Il Baek),조효제(Hyo-Jae Jo),이민준(Min-Jun Lee),임재환(Jae-Hwan Lim),이태경(Tae-Kyung Lee),김재희(Jae-Heui Kim),오태원(Tae-Won Oh) 한국해양공학회 2018 韓國海洋工學會誌 Vol.32 No.4
Recently, it was predicted that the size of offshore markets will grow as gas prices edge up. This paper presents experimental results for using strings as a suppression device on a circular cylinder and discusses the various data. A test model was used to investigate the role of strings by varying the thickness of the strings used to suppress a cylinder’s lateral force taking into account the effect of turbulence promoted. A substantial amount of experimental data were taken from experiments performed on cylinders at Reynolds number up to a maximum value of 105. The suppression of vortex shedding and a lateral force reduction of up to 70% were observed for the cylinder with strings.
수조실험을 통한 해저지반 굴삭용 워터젯 장비의 성능평가에 관한 연구
나경원(Kyoung-Won Na),조효제(Hyo-Jae Jo),백동일(Dong-Il Baek),황재혁(Jae-Hyuk Hwang),한성훈(Sung-Hoon Han),장민석(Min-Suk Jang),김재희(Jae-Heui Kim) 한국해양공학회 2015 韓國海洋工學會誌 Vol.29 No.6
The demand for subsea cables and pipelines that transfer marine energy resources onshore has recently increased. Laying these underground after trenching is one engineering method to stabilize exposed subsea cables and pipelines. This experimental study found the optimum conditions for operating two types of waterjet arms mounted on an ROV trencher. A waterjet arm for trenching the seabed was scaled down at a ratio of 1:6, and a comparative analysis was conducted using diverse parameters. The results of this research provide a practical fundamental database to assist in making decisions about the ROV trencher performance in advance.