• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.4
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• pp.236-243
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• 2013

Offshore wind turbines has to be proved against accidental events such as ship collision. In this study, ship collision fragility analysis of offshore wind turbine is done. Dynamic collision analysis is accomplished by considering soil foundation interaction and fluid structure interaction. Uncertainties due to ship weight and speed, angle are also considered. By analyzing dynamic response of offshore wind turbine, fragility curves are obtained for different damage levels. They can be used for restricting boat speed around the wind turbine and allowable size of the boat for inspection and for other purposes. Results of the fragility, it was confirmed fragility of collision speed of bulk ship of 30,000DWT and 850ton barge ship.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.3
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• pp.137-151
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• 1991

The motion of two-dimensional floating breakwaters with rectangular clots-section which are moored tautly in shallow water has been analyzed using a velocity potential matching method in which the fluid region is devided into sub-regions and then unknown coefficients of velocity potentials are determined from the continuity condition of mass and momentum flux of fluid at imaginary boundaries between sub-regions. The method originally suggested by Ijima et al.(1972) for the motion of submerged body has been modified to analyze the motion of floating body. The total fluid region has been divided into three sub-regions : the incident wave region, the transmitted wave region and the region below the floating breakwater. The restoring forces induced by mooring lines which were ignored by Ijima et al.(1972) have been modeled as linear springs with the initial tension effects. This method has been verified through the comparions with results from hydraulic expriments. Applications to various conditions of floating breakwater have been performed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.876-883
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• 2016

In this study, we selected CFRP to construct a canoe hull. A ship design was made using a commercial ship design program, SOLIDWORKS, and a flow analysis of the canoe on a free surface was calculated using STAR-CCM+. A flow field and waveform were obtained in this way. These results were used to check the resistant performance of the canoe. Results showed that if the draft is 0.09 m, it is safe to run at less than 4 m/s, and if draft is 0.24 m, it is safe to run at less than 2 m/s. Moreover, it was confirmed that those speeds can be made by two adults. The developed canoe, which is 20 % lighter in comparison with conventional FRP models, was briefly introduced in this paper.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.146-152
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• 2014

Design procedure of WEC (wave energy converter) using the heaving motion of a floating cylinder-type buoy coupled with LEG (linear electric generator) system is introduced. It is seen that the maximum power can actually be obtained at the optimal conditions ($c_{PTO}=b_T$, ${\omega}={\omega}_N$). Then, based on the developed theory, several design strategies are proposed to further enhance the maximum PTO (power take off), which includes the intentional mismatching with the heave natural frequency, which is 15% higher value than the peak frequency of input velocity spectrum. By using the intentional mismatching strategy, the generated power is actually increased and the corresponding draft as well as the required PTO damping value is significantly reduced, which is a big advantage in manufacturing the WEC with practical LEG (linear electric generator) system.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.1-7
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• 1994

As a subsequent work presented in Ref.[1] which deals with the global dynamic wave loads in the classification rules, further studies on such as the dynamic pressures above load waterline, motions and accelerations and other local design loads were carried out. Frequency domain 2D linear strip theory is employed and statistical analyses for the concerned ship responses were carried out for the 17 existing ships to derive simple and descriptive formula which can be used as a guidelines at preliminary design stage as well as a part of classification rules. The calculated results and thereby proposed formula are compared with those of other available data, and will be incorporated in the rules for steel ships of Korean Register of Shipping.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.66-72
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• 1994

For the reliable prediction of maneuverability of a ship, lots of captive model tests have been carried out for over 10 years. But the parameters appearing in the mathematical model are so versatile and showing complex characteristics, and it is still hard to establish the useful formulae that we can adopt directly in the design stage. In this paper, the most important parameters in the mathematical model. i.e.($1-\omega_P$) the effective wake fraction at propeller, and $\delta_R(\beta_R)$), the effective rudder inflow angles are investigated by the captive model tests at the circulating water channel. The model is tested at designed speed and at low speed, and the drafts at both full load and ballast load conditions are taken. Propeller thrusts and rudder normal forces are measured at the given drift angle and propeller revolution. These forces are used for the analysis of the effective flow velocity or flow direction, to the propeller or rudder.

• Journal of the Korean Geophysical Society
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• v.9 no.2
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• pp.105-112
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• 2006

We intend to increase in eficiency of the topographic monitoring of seabed or riverbed by combinedwith DGPS, RTK GPS and echo sounder. For this study, we defined the error corection of the echo sounder with the experiment of water tank, which is considered the characteristic of estuary riverbedand then we developed the s/w for 3-dimensional monitoring of estuary riverbed and aplied the s/wto field test and improved the various problems. On analyzing topography of estuary riverbed by combinedby the movement of survey vessel to the end of the transducer was eliminated by geometrical rearangementand we defined the corection formula, . The sounding error about the echo sounder and characteristic of estuary riverbed was found by understanding the relation of average diameter and residual error and we defined corection formula, Y=-0.0474*ln(X) -0.045 by the regression analysis. and then we verified applicability of corection formula. This study that by Visual Basic must be useful applied in the topographic analysis of the estuary riverbed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.965-971
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• 2017

The primary objective of this study was to assess the energy efficiency performance of an optimized hull form capable of saving energy based on existing vessels. The bow shape of existing vessels was investigated, giving consideration to design draft and speed. Resistance performances were also assessed for existing vessels according to operating conditions. Commercial CFD codes and model test materials were used to assess effective power. An optimized hull form with minimum resistance was selected given real operating conditions. The effective horsepower of existing and optimized vessels was estimated at three speeds. Resistance performance for an optimized vessel showed a 6 % improvement in effective horsepower at design speed (12 knots) compared to existing vessels. Quasi-propulsive efficiency employed experimental data, while energy efficiency performance was analyzed based on operating days, bunker fuel oil C cost, daily fuel oil consumption and specific fuel oil consumption. Energy efficiency performance for an optimized vessel showed a gain of 30 million won per year in reduced costs at design speed (12 knots) compared to existing vessels.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.122-122
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• 2023

한강 하구는 조석의 변화가 매우 크고 이로 인한 하상의 변화가 많이 발생하는 지역이다. 더불어 남북간 군사상황으로 인해 접근이 불가능하거나 어려운 지역이며, 이로인해 그동안 개발이 거의 이루어지지 않고 자연상태로 남아있다. 남북관계의 상황변화에 따라 그동안 한강 하구의 개발이나 보전에 대한 다양한 논의가 있었고, 그 중 뱃길 복원에 대한 이야기도 다양하게 진행되어 왔다. 하지만 아직까지 구체적으로 어떤 규모의 선박이 얼마동안 운행할 수 있는지에 대한 분석은 거의 이루어진 바가 없다. 본 연구에서는 한강 하구 신곡수중보 하류에서 공릉천 합류부 구간에 대한 주운 가능성을 분석하였다. 최근 하상측량 결과를 바탕으로 조석변화에 따라 형성되는 지점별 수심을 분석하였고 이를 토대로 형성되는 수로를 분석하였다. 선박 규모에 따라 필요로 하는 흘수와 수심을 이용하여 대상 구간에서 운행가능성을 분석하였다. 또한 이와 같이 형성된 수로가 안정적이지 않음을 하상변동 자료를 이용하여 제시하였다. 대상구간에서 조석변화에 따라 형성되는 수심과 선박 규모에 따른 필요수심을 비교 분석한 결과 대형 선박의 상시적 운행은 매우 제한적인 것으로 나타났다. 중소규모 선박의 경우에도 연간 운행 가능시간이 제한적인 것으로 나타나 일반적으로 추정하는 것보다 상업적인 대규모 주운의 가능성은 크지 않은 것으로 나타났다. 이 구간의 하상변동도 매우 큰 것으로 분석되었다. 지난 10년, 20년 동안의 장기적인 변화 뿐만아니라 1년 사이의 단기적인 변화도 크게 나타나 안정적인 수로 확보는 쉽지 않은 것으로 분석되었다. 한강 하구에서는 대규모 홍수가 발생하지 않더라도 조차가 큰 조석영향에 의해 하상이 지속적으로 변화하고 있는 것으로 추정된다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.789-797
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• 2021

The worldwide sizes of container ships are rapidly increasing. The container ship size in 2005, which was about 9,200 TEU has increased to 24,000 TEU in recent times. In addition to the increase in the sizes of the container ships, the arrivals/departures of large container vessels to/from Korea have also increased. Hence, the necessity for reviewing safe passage of such vessels is emphasized. In the present study, a 24,000 TEU container vessel was used as a model ship to calculate the under-keel clearance (UKC) at Gadeok Channel through which vessels must pass to arrive at Busan New Port, in accordance with the Korean Port and Fishing Port Design Standards and Commentary. In addition, the maximum allowable speed that meets UKC standards was calculated using various squat formulas, whose results were then compared with the current speed limit standards. The analysis results show that Busan New Port requires 10% marginal water depth, and the squat that meets this requirement is 0.95 m. Gadeok Channel requires 15% marginal water depth, and the squat that meets this requirement is 1.78 m; in this case, the maximum allowable speed is calculated as 15 kts. Busan New Port has set the speed limit as 12 kts, which is higher than the calculated 11 kts. Thus, speed limit reconsideration is required in terms of safety. However, the set speed limit for Gadeok Channel is 12 kts, which is lower than the calculated 15 kts. Thus, additional considerations may be provided to increase the speed limits for smooth navigational passage of vessels. The present study, however, is constrained by the fact that it reflects only a limited number of elements in the UKC and allowable speed calculations; therefore, more accurate UKC and safe speed values can be suggested based on extended studies to this research.