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노유호,김국현,조철희,김도엽 대한조선학회 2013 International Journal of Naval Architecture and Oc Vol.5 No.2
Floating production storage and offloading (FPSO) facilities are used at most of the offshore oil fields worldwide. FPSO usage is expected to grow as oil fields move to deeper water, thus requiring the reliability and stability of mooring wires and risers in extreme environmental conditions. Except for the case of predictable attack angles of external loadings, FPSO facilities with turret single point mooring (SPM) systems are in general use. There are two types of turret systems: permanent systems and disconnectable turret mooring systems. Extreme environment criteria for permanent moorings are usually based on a 100-year return period event. It is common to use two or three environments including the 100-year wave with associated wind and current, and the 100-year wind with associated waves and current. When fitted with a disconnectable turret mooring system, FPSOs can be used in areas where it is desirable to remove the production unit from the field temporarily to prevent exposure to extreme events such as cyclones or large icebergs. Static and dynamic mooring analyses were performed to evaluate the stability of a spider buoy after disconnection from a turret during cyclone environmental conditions.
싸이클론 환경에서 부이에 연결된 라이저의 안전성을 위한 무어링 설계 방법 연구
노유호(Yu-Ho Rho),조철희(Chul-Hee Jo),김도엽(Do-Youb Kim) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
FPSO는 부유식 원유생산설비에 대한 세계수요 중 가장 높은 비중을 차지하며 특히 해양 유전의 개발 추세가 천해에서 심해로 바뀌면서 FPSO의 필요성은 대두되었다. FPSO 터렛(turret)은 위치에 따라 internal turret과 external turret으로 구분할 수 있다. 그리고 극한 해양환경을 고려하여 FPSO의 service life까지 터렛과 무어링의 연결이 유지되는 permanent turret과 극한 해양 환경에서 무어링과 라이저의 연결을 끊고 다시 연결 할 수 있는d isconnectable turret으로 구분을 할 수 있다. 본 논문은 싸이클론과 같은 극한 해양환경에서 FPSO와 분리된 후 스파이더 부이에 연결된 라이저의 안전성을 확보하기 위하여 무어링 설계 방법에 연구하였. 비다싸이클론 해양환경에서 FPSO와 연결된 라이저의 안전성을 확보하기 위한 무어링 설계를 하고FP SO의 흘수(밸러스트 상태와 풀 밸러스트 상태)에 따른 라이저의 동적해석 후 싸이클론 해양환경에서FP SO와 분리된 스파이더 부이가 안전한 위치에서 운동하는지를 확인하였다.
조철희(Chul-Hee Jo),노유호(Yu-Ho Rho),이준호(Jun-Ho Lee),이강희(Kang-Hee Lee) 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5
Due to global warming, the need to secure an alternative resource has become more important nationally. Having very strong current on the west coast with up to 10 m tidal range, there are many suitable site for the application of TCP(Tidal Current Power) in Korea. To extract a significant quantity of power, a tidal current farm with a multi-arrangement is necessary in the ocean. The interactions between devices contribute significantly to the total power capacity. Thus, interaction problems needs to be investigated for generating maximum power in a specific field. The study of wake propagation is necessary to understand the evolution of the wake behind a turbine. This paper introduces the unsteady simulations for a tidal turbine wakes by CFD. The downstream wakes of computational models were compared with Jensen's wake model representing theoretical streamwise velocities.
조류발전용 수평축 터빈의 형상설계 및 가변 부하를 이용한 성능실험
조철희(Jo, Chul-Hee),노유호(Rho, Yu-Ho),이강희(Lee, Kang-Hee) 한국신재생에너지학회 2012 신재생에너지 Vol.8 No.1
Due to a high tidal range of up to 10 m on the west coast of Korea, numerous tidal current projects are being planned and constructed. The turbine, which initially converts the tidal energy, is an important component because it affects the efficiency of the entire system. Its performance is determined by design variables such as the number of blades, the shape of foils, and the size of a hub. To design a turbine that can extract the maximum power on the site, the depth and duration of current velocity with respect to direction should be considered. Verifying the performance of a designed turbine is important, and requires a circulating water channel (CWC) facility. A physical model for the performance test of the turbine should be carefully designed and compared to results from computational fluid dynamics (CFD) analysis. In this study, a horizontal axis tidal current turbine is designed based on the blade element theory. The proposed turbine's performance is evaluated using both CFD and a CWC experiment. The sealing system, power train, measuring devices, and generator are arranged in a nacelle, and the complete TCP system is demonstrated in a laboratory scale.
강한 전단 해류 환경에서 동적 전력케이블의 VIV 피로해석 절차에 관한 기초 연구
심천식,김민석,김철민,노유호,이재복,채광수,김강호,정다슬 대한조선학회 2023 大韓造船學會 論文集 Vol.60 No.5
The subsea power cables are increasingly important for harvesting renewable energies as we develop offshore wind farms located at a long distance from shore. Particularly, the continuous flexural motion of inter-array dynamic power cable of floating offshore wind turbine causes tremendous fatigue damages on the cable. As the subsea power cable consists of the helical structures with various components unlike a mooring line and a steel pipe riser, the fatigue analysis of the cables should be performed using special procedures that consider stick/slip phenomenon. This phenomenon occurs between inner helically wound components when they are tensioned or compressed by environmental loads and the floater motions. In particular, Vortex-induced vibration (VIV) can be generated by currents and have significant impacts on the fatigue life of the cable. In this study, the procedure for VIV fatigue analysis of the dynamic power cable has been established. Additionally, the respective roles of programs employed and required inputs and outputs are explained in detail. Demonstrations of case studies are provided under severely sheared currents to investigate the influences on amplitude variations of dynamic power cables caused by the excitation of high mode numbers. Finally, sensitivity studies have been performed to compare dynamic cable design parameters, specifically, structural damping ratio, higher order harmonics, and lift coefficients tables. In the future, one of the fundamental assumptions to assess the VIV response will be examined in detail, namely a narrow-banded Gaussian process derived from the VIV amplitudes. Although this approach is consistent with current industry standards, the level of consistency and the potential errors between the Gaussian process and the fatigue damage generated from deterministic time-domain results are to be confirmed to verify VIV fatigue analysis procedure for slender marine structures.
1.2MW급 부유식 조류발전 시스템 모듈의 계류 안정성 평가
조철희(Chul-Hee Jo),노유호(Yu-Ho Rho),박노식(Ro-Sik Park),홍성준(Seong-Jun Hong) 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.5
To apply a tidal current power in deep water region, a floating module mounted with the turbine together with control system is one of the feasible options. This is because that the cost of conventional pile fixed structure fabrication and Installation increases sharply with the water depth. To stabilize the module m high speed current region, it is critical to design the appropriate mooring system together with the module dynamic behavior. The conceptual research has been conducted to confirm the stability of a mooring system for a 1.2 MW floating tidal current power generation module. The semi submersible module configuration has been adopted to maximize the dynamic stability w.r.t. strong current The 4 point chain mooring concept is applied in the study. The ANSYS AQWA software is used to analysis the mooring tension and excursion of the module under the external forces generated by wind, wave, and current.