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홍도천,홍사영,성홍근,Hong, Do-Chun,Hong, Sa-Young,Sung, Hong-Gun The Society of Naval Architects of Korea 2010 大韓造船學會 論文集 Vol.47 No.3
A three-dimensional time-domain calculation method is of crucial importance in prediction of the motions and wave loads of a ship advancing in a severe irregular sea. The exact solution of the free surface wave-ship interaction problem is very complicated because of the essentially nonlinear boundary conditions. In this paper, an approximate body nonlinear approach based on the three-dimensional time-domain forward-speed free-surface Green function has been presented. The Froude-Krylov force and the hydrostatic restoring force are calculated over the instantaneous wetted surface of the ship while the forces due to the radiation and scattering potentials over the mean wetted surface. The time-domain radiation and scattering potentials have been obtained from a time invariant kernel of integral equations for the potentials which are discretized according to the second-order boundary element method (Hong and Hong 2008). The diffraction impulse-response functions of the Wigley seakeeping model advancing in transient head waves at various Froude numbers have been presented. A simulation of coupled heave-pitch motion of a long rectangular barge advancing in regular head waves of large amplitude has been carried out. Comparisons between the linear and the approximate body nonlinear numerical results of motions and wave loads of the barge at a nonzero Froude number have been made.
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 (ŋH>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.
불연속 고차 경계요소법을 사용한 근접계류 선체 GAP 자유표면 공진 및 시간평균 표류력 해석
홍도천(Do-Chun Hong),홍사영(Sa-Young Hong),남보우(Bo-Woo Nam) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.11
The formulation based on the conventional multiple floating body hydrodynamics together with a nine-node discontinuous higher order boundary element method (9dHOBEM) has been used to obtain numerical results of the potential boundary value problems related to two vessels floating side-by-side in close proximity. An artificial damping parameter as used in the sloshing analysis (Zalar et al., 2007) has been introduced into the body boundary condition in order to reduce unrealistic wave elevations in the gap at resonant frequencies. The potential and its derivative on the wetted surface are calculated according to the 9dHOBEM numerical scheme. Numerical results of drift forces of a FPSO and a shuttle tanker floating side-by-side at a 4- meter gap in head seas have been presented and compared to the experimental results presented by Hong et al. (2002).