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유한요소법을 이용한 수직 실린더에 작용하는 극한 파랑력 해석
경조현(Jo Hyun Kyoung),홍사영(Sa Young Hong),성홍근(Hong Gun Sung) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
Finite element method is applied to predict wave loads on a vertical cylinder under freak wave. As a mechanism for freak wave generation, a frequency-focused unidirectional wave is adopted in three-dimensional numerical wave tank. The mathematical formulation is made in the scope of potential theory with fully nonlinear free surface condition. As a numerical method, finite element method based on variational principle is adopted. Comparisons between numerical results and the experiment data are made.
유탄성 응답을 고려한 수직 실린더에 작용하는 극한 파랑 충격력 수치해석
경조현(Jo Hyun, Kyoung),홍사영(Sa Young, Hong),김병완(Byoung Wan, Kim) 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.3 No.1
The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as freak wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method, based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition. 해양구조물에 유기되는 파랑력과 해양파에 의한 해양구조물의 운동특성에 대한 연구는 선형이론에 근거한 통계적인 방법에 의해 꾸준히 연구되어왔다. 이러한 연구는 선형이론의 제한성으로 인해 파 스펙트럼의 극한에 해당하는 극한파에 대해서는 적용하기 어려운 점이 있다. 본 연구에서는 간단한 구조물에 대하여 극한파에 의한 파장력을 추정하는 수치기법을 개발하였다. 극한파는 선형 파랑 집중법을 이용하여 수치적으로 구현하여 바닥면에 고정된 수직 실린더에 작용하는 파장력을 추정하였다. 또한 수직 실린더의 유탄성 응답을 고려하여 강체인 경우와 탄성체의 경우에서 극한파에 의한 파랑력 변화를 고찰하였다.
경조현(JO-HYUN KYOUNG),홍사영(SA-YOUNG HONG),홍도천(DO-CHUN HONG) 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.4
A numerical analysis is made to investigate the wave absorption efficiency of a OWC-type wave power generator. Energy absorption by an OWC(Oscillating Water Column) air-chamber is computed in regular waves, taking account of the oscillating surface-pressure, due to pressure drop, across the duct of the air chamber. The problem is formulated in the scope of potential theory and solved by the Localized Finite Element Method(LFEM), based on the classical variational principle. The efficiency of energy absorption is investigated by changing wave conditions, sea-bottom slope and pressure drop coefficient.
홍사영(Hong, Sa-Young),경조현(Kyoung, Jo-Hyun),조석규(Cho, Seok-Kyu),김병완(Kim, Byoung-Wan) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.1
In this paper, the modified direct method employing beam transformation technique is proposed in order to efficiently calculate hydroelastic responses of floating structure. Since the proposed method expresses the displacements of three-dimensional structure with those of transformed beam which leads to small number of equations of motion, the method is numerically efficient compared to the conventional direct method. To verify the efficiency of the proposed method, a 500 m-long floating structure under wave loads is considered in numerical example. Displacements, bending moments, torsion moments and shear forces are calculated and computing time is examined. The results are also compared with those of the conventional direct method.
김병완(Kim, Byoung-Wan),경조현(Kyoung, Jo-Hyun),홍사영(Hong, Sa-Young),조석규(Cho, Seok-Kyu),이인원(Lee, In-Won) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.1
Two modified versions of subspace iteration method using accelerated starting vectors are proposed to efficiently calculate free vibration modes of structures. Proposed methods employ accelerated Lanczos vectors as starting iteration vectors in order to accelerate the convergence of the subspace iteration method. Proposed methods are divided into two forms according to the number of starting vectors. The first method composes 2p starting vectors when the number of required modes is p and the second method uses 1.5p starting vectors. To investigate the efficiency of proposed methods, two numerical examples are presented.