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파랑중 컨테이너선과 하역선의 연결장치에 작용하는 하중계산
홍도천(Do-Chun Hong),김용욱(Yong-Yook Kim),한순흥(Soonhung Han) 한국해양환경·에너지학회 2009 한국해양환경공학회 학술대회논문집 Vol.2009 No.11월
The hydrodynamic interaction of two floating bodies in waves freely floating or connected by a rigid link is studied by using a boundary element method in the frequency-domain. The exact two-body hydrodynamic coefficients of added mass, wave damping and exciting force are calculated from the radiation-diffraction potential solution of the improved Green integral equation associated with the free surface Green function. The irregular frequencies in the conventional Green integral equation make it difficult to predict the physical resonance of the fluid in the gap between two bodies floating side by side. However, the improved Green integral equation employed in this study is free of irregular frequencies and always yields the exact solution of the multi-body radiation-diffraction potential boundary value problem. The 6 degree-of-freedom motions of two bodies freely floating side by side or connected parallel by a rigid link have been calculated for the incident wave frequencies ranging from 0.1 to 5 radians per second in head, left and right bow quartering seas. The 6-component load of the rigid link have also been presented.
홍도천(Do-Chun Hong),현범수(Beom-Soo Hyun),홍사영(Sa-Young Hong) 한국해양공학회 1992 韓國海洋工學會誌 Vol.6 No.1
The hydrodynamic performance of a floating-type OWC (Oscillating Water Column) chamber is studied numerically and experimentally in this study. The numerical approach based on two-dimensional linear theory of floating wave absorber was attempted to design an efficient wave energy absorber, while model test was performed in a wave basin to test a performance of designed model and validate the reliability of developed numerical code. The focus of study is placed mainly on the experimental study to evaluate the principal characteristics of the designed OWC chamber in regular waves. The effects of the variation of wave height on OWC device and of air pressure inside chamber are also presented. Finally, the measured results were compared with computed ones, and it was shown that the designed chamber works with high efficiency (ŋ<SUB>H</SUB>>1) over most of wave lengths covered by present study. It is therefore concluded that the developed code is capable of being successfully employed to design OWC chambers at various ocean environments, even though there exist some minor discrepancies between measured and computed results.
부유식 해양구조물에 작용하는 시간평균 파표류력에 관한 고찰
홍도천(DO-CHUN HONG) 한국해양공학회 2002 韓國海洋工學會誌 Vol.16 No.3
Formulation of the far-field method for the prediction of time-mean hydrodynamic force and moment acting on a 3-D surface-piercing body in waves is reviewed. It is found that the inequality between the weight of the floating body and its buoyancy force permits the replacement of the fluid particles inside the control surface by the fluid particles outside the control surface. Under such circumstances, momentum exchanges across the control surface make the time-mean value of the time rate of the momentum of the fluid inside the control surface non-vanishing. It is a second-order quantity which is hard to calculate by the far-field method. The drift forces and moments on half-immersed ellipsoids are calculated by both the far-field method and the near-field method. The discrepancy between two numerical results is presented and discussed.
홍도천(DO-CHUN HONG) 한국해양공학회 2002 韓國海洋工學會誌 Vol.16 No.3
The motion of a floating OWC chamber in waves is studied taking account of fluctuating air pressure in the air chamber. An atmospheric pressure drop occurs across the upper opening of the chamber which causes not only hydrodynamic but also pneumatic added mass and damping forces to the floating chamber. A velocity potential in the water due to the free surface oscillating pressure patch is added to the conventional radiation-diffraction potential problem. The potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine Green function while the outer problem with the Kelvin Green function. The two integral equations are solved simultaneously by making use of a matching boundary condition at the lower opening of the chamber to the outer water region. The chamber motion in the frequency domain is calculated for various values of parameters related to the atmospheric pressure drop. The present methods can also be used for the analysis of air-cushion vehicle motion as well as for the design of a floating OWC wave energy absorber.
On the Negative Drift Force Acting on a Freely Floating Surface-Piercing Cylinder
Do-Chun Hong(洪道天) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.3
수면상에 떠있는 2차원 물체에 작용하는 시간평균 표류력 및 표류모오멘트를 비점성 선형 포텐셜 이론을 사용하여 계산하는 방법에 대하여 검토하였다. 부유체 접수면상의 압력을 직접 적분하여 구한 수평방향 표류력이 특정주파수 부근에서 음의 값을 보이고 있다. 이는 무한원 방에서의 에너지 보전방법에 의한 표류력이 항상 양의 값을 취한다는 기존 이론과 상이하다. 본 논문에서, 이러한 차이가 부유체의 횡요 및 상하동요에 기인한 복원력의 성분과 횡요와의 연성효과에 의하여 발생하였음을 규명하였다. 이는 횡요가 있는 경우, 표류력을 산출하는 기존의 무한원방 방법에 결함이 있음을 보이고 있다. 이에 반하여 기존의 접수면압력 직접적분 방법은 부유체에 작용하는 시간평균 표류력 및 표류모오멘트를 모든 주파수에 대하여 정확하게 산출한다고 결론지울 수 있다.
Hybrid 적분방정식을 사용한 Flap-Harbour 복합체파 에너지 흡수효율 추정
홍도천(DO-CHUN HONG),김현주(HYEON-JU KIM) 한국해양공학회 2000 韓國海洋工學會誌 Vol.14 No.2
Wave energy absorption by a flap equipped with a harbor in a water of finite depth is studied. The wave potential is calculated by a hybrid integral equation consisting of Green integral equations associated with Rankine and Kelvin Green functions. The absorbed wave energy is calculated by both the near-field and far-field methods. The present methods can be used for the design of a flap-harbor wave energy absorber since the numerical results by the two methods are in good agreement.