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박태현(T. H. Park),문중수(J. S. Moon),이인혜(I. H. Lee),심우승(W. S. Sim),신현수(H. S. Shin) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
Considering the wave impact load is required in the structural assessment of FPSOs. The importance of the wave impact load on offshore structures in the deep water has increased after the casualty by the wave impact was reported in FPSO installed in the North Sea. The wave impact load on offshore structures can be divided into the green water impact load and the wave slamming impact load. It is known that these wave impact loads show the strong nonlinear characteristics. On the other hand, the classification rule is not sufficiently specified enough to assess the wave impact load. Therefore, more accurate evaluation method of the nonlinear wave impact load is necessary for the safe design of offshore structures. In this paper, the estimation procedures of the green water impact load and the wave slamming impact load are proposed for considering the wave impact load in the design step of offshore structures. These estimation procedures were verified by comparing with the design impact loads of the previous FPSO projects.
Nonlinear effect on wave loads of large ships in time domain
Kim, Mun-Sung,Park, Jong-Jin,Kim, Byung-Woo,Eom, Jae-Kwang The Society of Naval Architects of Korea 2011 International Journal of Naval Architecture and Oc Vol.3 No.1
As sea state harsher in the ocean space, more large motion and wave loads occurs on ships hull by non-linear phenomena. To consider nonlinear effect on ships hull in the structural design verification, the direct calculation method with numerical approach is used rather than rule values for the reliable accuracy. In this paper, the non-linear wave loads analysis in time domain is performed by using a Rankine Panel Method together with numerical schemes. Linear calculations have been carried out based on DNV CSA-2 notation to generate the motion responses and wave loads of large ships. By short and long term analysis, the design wave amplitudes are selected for the nonlinear analysis. The maximum wave induced bending moment in hogging and sagging conditions are calculated in the nonlinear analysis. Also, the green water effect on the wave induced vertical bending moment was investigated. The results show the vertical bending moments are more influenced by green water in sagging condition than in hogging condition due to green water loading.
Nonlinear effect on wave loads of large ships in time domain
김문성,박종진,김병우,엄재광 대한조선학회 2011 International Journal of Naval Architecture and Oc Vol.3 No.1
As sea state harsher in the ocean space, more large motion and wave loads occurs on ships hull by non-linear phenomena. To consider nonlinear effect on ships hull in the structural design verification, the direct calculation method with numerical approach is used rather than rule values for the reliable accuracy. In this paper, the non-linear wave loads analysis in time domain is performed by using a Rankine Panel Method together with numerical schemes. Linear calculations have been carried out based on DNV CSA-2 notation to generate the motion responses and wave loads of large ships. By short and long term analysis, the design wave amplitudes are selected for the nonlinear analysis. The maximum wave induced bending moment in hogging and sagging conditions are calculated in the nonlinear analysis. Also, the green water effect on the wave induced vertical bending moment was investigated. The results show the vertical bending moments are more influenced by green water in sagging condition than in hogging condition due to green water loading.
김문성(Mun Sung Kim),박종진(Jong Jin Park),안영규(Young Kyu Ahn),김홍수(Hong Su Kim),전호환(Ho Hwan Chun) 한국해양공학회 2015 韓國海洋工學會誌 Vol.29 No.4
With the increases in oil and gas prices, and energy consumption, drillship construction has increased during the last decade. A drillship using a dynamic positioning (DP) system to maintain its position and heading angle during drilling operations. In addition, a drillship is equipped with a moonpool structure to allow its drilling systems to be operated in the midship section. A drillship for the North Sea is specially designed to endure harsh environmental loads. For safe operation in the North Sea, the drillship should have good motion response and robust hull strength. A break water should be considered on the bow and side deck to prevent the green water on deck phenomenon from oncoming waves. In addition, the moonpool should be designed to reduce the speed loss and resonance motion. In this study, the hydrodynamic characteristics of a drillship for the North Sea were examined in relation to the motion, wave loads, green water, and moonpool resonance in the initial design stage.
김문성(M. S. Kim),박종진(J. J. Park),안영규(Y. K. Ahn),김병우(B. W. Kim),엄재광(J. K. Eom) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
고유가와 에너지 소비 증가로 드릴쉽(drillship)의 건조가 활발해 지고 있다. 드릴쉽은 위치와 선수 각을 유지하기위한 목적으로 DP(Dynamic Positioning) 시스템을 장착하고 있다. 또한 시추시 작업 편의성을 위해 선박의 중앙부에 moonpool을 보유하고 있다. 설계 대상인 드릴쉽은 파도가 상당히 거친 북해용으로서 노르웨이와 바렌츠 해역까지 투입되도록 설계되었다. 드릴쉽이 거친 해상조건에서 DP 시스템을 통해 위치 및 선수 각을 유지하면서 작업하기 위해서는 운동 성능이 우수해야 하며 파도가 거친 북해에서도 견딜 수 있는 강도로 구조설계가 되어야 한다. 또한 DP 시스템으로 유지가 가능한 선수 각 범위 내에서 사파로 유입되는 측면 green water에 대비한 break water 설계를 검토해야 한다. 마지막으로 선체 중앙부에 위치한 moonpool로 인한 저항증가와 내부의 유동 문제를 설계 전 검토하여 moonpool 유동 억제 장치를 설치해야 한다. 본 논문에서는 북해용 드릴쉽을 설계하기 위해서 수행한 운동, 파랑하중 해석, green water 해석 및 모델 테스트 그리고 moonpool 내부 유동에 의한 공진 현상 시뮬레이션을 소개한다.
규칙파 중 갑판침입수 충격하중 감소를 위한 선수형상 설계
하윤진(Yoon-Jin Ha),이영길(Young-Gill),정광열(Kwang-Leol Jeong) 한국해양공학회 2012 韓國海洋工學會誌 Vol.26 No.4
In this research, the relationship between the bow shape and green water phenomenon on the bow deck of an FPSO was studied using an experimental method. A 140,000 DWT FPSO was used as the objective hull form in the present research. The incident waves were regular types. The heights were 1.0 and 1.5 times the freeboard, and the length was equal in size to LBP. The wave heights and pressures on the deck were measured in experiments. Model tests were performed to determine the effects of bow flare angles, bow shapes, and a forecastle deck. The free heave and pitch conditions were applied to the models in these experiments. From the results of the model tests, an optimized bow shape was designed, which was found to decrease the green water impact loading. The results of this research could be used as fundamental data in the design of a bow shape.
CFD as a seakeeping tool for ship design
김성은 대한조선학회 2011 International Journal of Naval Architecture and Oc Vol.3 No.1
Seakeeping analysis has progressed from the linear frequency-domain 2D strip method to the nonlinear timedomain 3D panel method. Nevertheless, the violent free surface flows such as slamming and green water on deck are beyond the scope of traditional panel methods based on potential theory. Recently, Computational Fluid Dynamics (CFD) has become an attractive numerical tool that can effectively deal with the violent free surface flows. ABS, as a classification society, is putting forth a significant amount of effort to implement the CFD technology to the advanced strength assessment of modern commercial ships and high-speed naval craft. The main objective of this study is to validate the CFD technology as a seakeeping tool for ship design considering fully nonlinear three-dimensional slamming and green water on deck. The structural loads on a large container carrier were successfully calculated from the CFD analysis and validated with segmented model test measurements.
CFD as a seakeeping tool for ship design
Kim, Sun-Geun Peter The Society of Naval Architects of Korea 2011 International Journal of Naval Architecture and Oc Vol.3 No.1
Seakeeping analysis has progressed from the linear frequency-domain 2D strip method to the nonlinear timedomain 3D panel method. Nevertheless, the violent free surface flows such as slamming and green water on deck are beyond the scope of traditional panel methods based on potential theory. Recently, Computational Fluid Dynamics (CFD) has become an attractive numerical tool that can effectively deal with the violent free surface flows. ABS, as a classification society, is putting forth a significant amount of effort to implement the CFD technology to the advanced strength assessment of modern commercial ships and high-speed naval craft. The main objective of this study is to validate the CFD technology as a seakeeping tool for ship design considering fully nonlinear three-dimensional slamming and green water on deck. The structural loads on a large container carrier were successfully calculated from the CFD analysis and validated with segmented model test measurements.