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Dynamic Response and Reliability of Six-Leg Jack-Up Type Wind Turbine Installation Vessel
Heo, Sanghwan,Koo, Weoncheol,Park, Min-Su World Scientific Publishing Company 2017 International journal of structural stability and Vol.17 No.3
<P>A fast, reliable and optimized numerical procedure of the hydrodynamic response analysis of a slender-body structure is presented. With this method, the dynamic response and reliability of a six-leg jack-up-type wind turbine installation vessel under various environmental conditions is analyzed. The modified Morison equation is used to calculate the wave and wind-driven current excitation forces on the slender-body members. The Det Norske Veritas (DNV) rule-based formula is used to calculate the wind loads acting on the superstructure of the jack-up leg. From the modal analysis, the natural period and standardized displacement of the structure are determined. The Newmark-beta time-integration method is used to solve the equation of motion generating the time-varying dynamic responses of the structure. A parametric study is carried out for various current velocities and wind speeds. In addition, a reliability analysis is conducted to predict the effects of uncertainty of the wave period and wave height on the safety of structural design, using the reliability index to indicate the reliability of the dynamic response on the critical structural members.</P>
해저파일-지반 상호작용을 고려한 잭업 레그의 동적 응답 해석
허상환(Sanghwan Heo),구원철(Weoncheol Koo),박민수(Min-Su Park) 한국신재생에너지학회 2016 신재생에너지 Vol.12 No.1
Using the substructure method, numerical models of pile-soil interaction of diagonal and diamond types of jack-up legs were developed for dynamic response analysis. Wave and current forces acting on the leg were calculated using the modified Morison equation. Wind load was computed using the DNV formula. Modal analysis was performed to estimate the eigenvalues of the structure. The Newmark-beta method was used to calculate the dynamic behaviors of the structure in the time domain analysis. Maximum displacement and bending stress were computed for each type of leg. Reliability analysis was carried out for both types of legs to obtain a reliability index for the uncertainty of input wave periods.
Analysis of Dynamic Response Characteristics for 5 MW Jacket-type Fixed Offshore Wind Turbine
Jaewook Kim,Sanghwan Heo,WeonCheol Koo 한국해양공학회 2021 韓國海洋工學會誌 Vol.35 No.5
This study aims to evaluate the dynamic responses of the jacket-type offshore wind turbine using FAST software (Fatigue, Aerodynamics, Structures, and Turbulence). A systematic series of simulation cases of a 5 MW jacket-type offshore wind turbine, including wind-only, wave-only, wind & wave load cases are conducted. The dynamic responses of the wind turbine structure are obtained, including the structure displacement, rotor speed, thrust force, nacelle acceleration, bending moment at the tower bottom, and shear force on the jacket leg. The calculated time-domain results are transformed to frequency domain results using FFT and the environmental load with more impact on each dynamic response is identified. It is confirmed that the dynamic displacements of the wind turbine are dominant in the wave frequency under the incident wave alone condition, and the rotor thrust, nacelle acceleration, and bending moment at the bottom of the tower exhibit high responses in the natural frequency band of the wind turbine. In the wind only condition, all responses except the vertical displacement of the wind turbine are dominant at three times the rotor rotation frequency (considering the number of blades) generated by the wind. In a combined external force with wind and waves, it was observed that the horizontal displacement is dominant by the wind load. Additionally, the bending moment on the tower base is highly affected by the wind. The shear force of the jacket leg is basically influenced by the wave loads, but it can be affected by both the wind and wave loads especially under the turbulent wind and irregular wave conditions.
김재욱(Jaewook Kim),허상환(Sanghwan Heo),구원철(Weoncheol Koo) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.5
해상 풍력 발전기와 관련된 연구는 현재 세계에 많은 관심을 받는 분야 중 하나이며 기술적 문제를 예측하고 해결하기 위해 다양한 연구가 진행되고 있다. 이러한 문제 해결을 위해 해상 풍력 발전기의 동적 응답을 수치 해석적 방법으로 예측하는 것이 중요한 해결법 중 하나로 제시되고 있다. 본 연구에서는 FAST 소프트웨어를 이용하여 파랑과 풍속의 조건에 따른 5MW급 자켓 타입 고정식 해상 풍력 발전기의 동적 응답을 분석하고자 한다. FAST 소프트웨어는 NREL (National Renewable Energy Laboratory)에서 제공하는 DOS 인터페이스의 오픈 소스 코드이다. FAST를 활용하여 풍속만 존재할 때, 입사파만 존재할 때, 풍속과 입사파가 동시에 적용될 때에 대한 여러 입력조건의 조합을 수치 시뮬레이션 하여 고정식 해상 풍력 발전기의 운동 성능을 각 주파수별로 분석하고 그 의미를 해석하였다. 수치해석을 통해 다음과 같은 동적 응답 결과의 분석을 수행하였다. - 고정식 해상 풍력 발전기의 6자유도 운동 - 발전기 운행 시 로터 속도 / 발전기 추력 / 나셀 가속도 - 타워 상, 하단에 발생하는 굽힘 모멘트 및 전단 응력 - 자켓 하부 구조물에 작용하는 반력 Even though offshore wind turbine is one of the hot topics in the world, the research on offshore wind turbine is yet enough and many technical problems are still waiting for resolutions. Among these technical problems, prediction of the dynamic response of an offshore wind turbine using numerical method is the one of the most critical ones. This research aims to investigate and analyze the dynamic responses of a 5MW jacket-type offshore wind turbine using FAST software. FAST software is an open source code of DOS interface provided by NREL (National Renewable Energy Laboratory). Using FAST, numerical simulation of a combination of multiple input conditions such as wind only, wave only, and combined wind and wave are performed. Then, the responses of a fixed offshore wind turbine for various input combinations are analyzed. Through numerical analysis, the following dynamic response results were analyzed. - 6 DOF motions of jacket-type offshore wind turbine - Rotor speed / Thrust force / Nacelle acceleration - Bending moments and shear force at tower top and tower bottom - Reaction force on jacket sub-structure.
한국해양환경을 고려한 부유식 마리나 구조물의 운동성능 향상에 관한 연구
김동민(Dong-Min Kim),허상환(Sanghwan Heo),구원철(Weoncheol Koo) 한국해양공학회 2019 韓國海洋工學會誌 Vol.33 No.1
The aim of this study was to improve the vertical motion performance of floating marina structures and to optimize the shapes of the structures for the Korea coastal environment. The floating body is connected to a plate-shaped submerged body through a connecting line under the water that has a stiff spring that serves to reduce the heave response. This system, which has two degrees of freedom, was modelled to analyze the interaction between the floating body and the submerged body. The vertical motion of the two-body system was compared with the motion of a single body to verify that the system could perform as an optimized model.