• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.250-253
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• 2001

This paper describes the effect of step bilge on motion characteristics of FPSO. The purpose of the present study is to investigate motion responses of FPSO with two types of step bilge. Model test result shows that the performance of the bottom type step bilge, that is designed to avoid collision, is as good as that of the side type step bilge.

• Journal of Ocean Engineering and Technology
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• v.16 no.1
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• pp.1-7
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• 2002

본 논문에서는 선체 하부에 moonpool과 bilge step을 장착한 새로운 개념으의 LNG-FPSO를 운동감소와 cargo, operation tank의 슬로싱 현상의 관점에서 기술하였다. LNG-FPSO의 주요제원은$L\times B\times D\times t(design)=270.0\times51.0\times32.32\times13.7(m)$ 이고 적용조건은 total corgo capacity of 161KT at 98% loading condition 이다. LNG-FPSO의 운동감소의 목적으로 2개의 moonpool과 선체하부 bilge 부분에 사각 step을 장착하였다. LNG-FPSO의 운동해석을 위해 단순화된 경계조건을 만족하는 선형화된 3차원 diffraction theory를 사용하였고 LNG-FPSO의 연성된 6-자유도 운동응답을 계산하였다. LNG-FPSO의 정확한 Roll 운동을 추정하기 위해 점성효과는 Himeno(1981)가 제안한 경험식을 사용하였다. Moonpool의 크기에 따른 운동감소의 경향을 파악하기 위해 이론적 계산과 실험적 방법으로 수행하였다. Moonpool 크기와 bilge step의 효과를 최적화하기 위해 총9가지의 case를 설정하였다. 이론 및 실험 결과로부터 본 LNG-FPSO는 moonpool과 bilge step의 장착으로 인한 감쇠력의 증가로 운동성능이 우수하다. 본 LNG-FPSO의 운동 응답중, 특별히 roll 운동이 다른 drillship, shuttle tanker등의 선박과 비교하여 상당히 작았고 이는 moonpool과 blige step의 장착으로 인한 효과로 판단된다. Cargo tank와 operation tank 크기를 검토 하기 위해 불규칙 해상중 sloshing 해석을 chamfer를 갖는 LNG-FPSO의 No.2, No.5 tank 벽면의 압력 분포와 자유표면의 time history에 초점을 맞추어 수행하였다. 최종적으로 tank 크기를 최적화 하였고 최적화된 tank는 선수사파와 횡파상태의 모든 filling에서 공진현상과 충격압력이 발생하지 않음을 확인하였다.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.5 no.1
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• pp.22-28
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• 2002

A New concept for the LNG-FPSO ship, with moonpool and bilge step in bottom, is proposed. This concept is investigated with regard to motion reduction and sloshing phenomena of the cargo and operation tanks. The principal dimensions of the ship are $L\timesb B\times D\times t(design)=270.0\times51.0\times32.32\times13.7(m)$, with a total cargo capacity of 161KT; a 98% loading condition is considered for this study. The moonpools and rectangular step at the bilge have been designed for the purpose of decreasing the motion within the tank. For the motion analysis, linearized three-dimensional diffraction theory, with the simplified boundary condition was used. The six-degree of freedom coupled motion responses were calculated for the LNG-FPSO ship. Viscous effects on the roll motion responses of a vessel were taken into account in this calculation program, using an empirical formula suggested by Himeno(1981). The case study for the moonpool size has been conducted using theoretical estimation and the experimental method. For the optimization of the moonpool size and effect of the bilge step, 9 cases of its size, both with and without bilge step, were involved in the study. no motion responses, especially roll motion, for the designed LNG-FPSO ships are much lower than those of other drill ships and shuttle tankers. The limit criterions are satisfied. To check the cargo tank and operation tank sizes, we performed a sloshing analysis in the irregular waves which focuses on the pressure distribution on the tank wall and the time history of pressure and free surface for No.2 and 5 tanks of LNG-FPSO with chamfers. Finally, optimum tank sire was estimated.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.197-200
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• 2002

In this paper, roll damping coefficients for a non-conventional cross section, which is herein named as 'step' model, are investigated numerically and experimentally. Experiments are extensively carried out to estimate the roll damping coefficients. Numerical estimations are also made with the help of numerical codes. For convenience, the roll damping is divided into wave-making component and viscous component. The wave-making component is determined using a potential code and the viscous component using a viscous flow code, in which the fluid domain is taken as unbounded. In order to validate the present approach, a typical cross section with bilge is considered and our results are compared with published data. The comparison shows a good agreement qualitatively. For the step model, numerical results are compared well with experimental data besides some quantitative discrepancies at a certain range of frequency. It is thought that the discrepancy might be caused by the ignorance of the free surface in viscous computations. It is found in the case of the step model that not only the viscous component but also the wave component increases considerably compared to the section with bilge.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.189-195
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• 2000

New concept of LNG-FPSO ship with moonpool and bilge step in bottom is considered and investigated in the point of motion reduction and sloshing phenomena of the cargo and operation tanks. The cargo capacity of the ship of which principle dimensions is L x B x D x t(design) =270.0 x 51.0 x 32.32 x 13.7(m) 16K at 98% loading condition. The two moonpools and rectangular step at bilge part are setted up specially for getting the effect of motion decrease. For the motion analysis, linearized three dimensional diffraction theory with the simplified boundary conditions is used. The six-degree of freedom coupled motion responses are calculated for the LNG-FPSO ship. Viscous effects on the roll motion responses of a vessel are taken into account in this calculation program using an empirical formula suggested by Ikeda, Himeno and Tanaka is used. The case study for the moonpool size had been carried out by theoretical estimation and experimental method. For the optimization of the moonpool size and effect of the step, 9 cases of its size and with and without step are considered. From the results of calculation and experiment, it can be concluded that this designed LNG-FPSO ship have possibility to carry out her missions in the rough sea as for the owner's demand waves condition. The motion responses, especially roll motion, for the designed LNG-FPSO ship are much lower than those of another drillship and shuttle tanker and limit criterions are satisfied. For the check of the cargo tank and operation tank sizes we have performed sloshing analysis in the irregular waves which focuses on the pressure distribution on the tank wall and the time history of pressure and free surface for No.2 and No5. tanks of LNG-FPSO with chamfers. Finally we got the tank size which has no resonance and no impact pressure in all filling in the bow quartering and beam sea.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.2
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• pp.109-123
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• 2008

The present paper presents the CFD result for a beam wave test case. An ONR tumblehome ship model with bilge keels is used. The beam wave test is for zero forward speed and roll and heave 2DOF with wave slope $a_k=0.156$ and wavelength ${\lambda}=1.12L_{PP}$, with $L_{PP}$ the ship length. The problems is solved numerically with an unsteady Reynolds averaged Navier-Stokes approach. The free surface flow is computed using a single-phase level-set method and the motions in each time step are integrated using a predictor-corrector iteration approach which uses dynamic overset grids moving with relative ship motion. The predicted CFD results for motions and forces are compared with experimental data, showing a reasonable agreement.

• Restorative Dentistry and Endodontics
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• v.45 no.2
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• pp.13.1-13.10
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• 2020

Objective: The aim of this study was to evaluate the influence of different modeling agents on the surface microhardness (Vickers hardness number; VHN), roughness (Ra), and color change (ΔE) of a nano-hybrid composite with or without exposure to discoloration by coffee. Materials and Methods: Sixty-four cylinder-shaped nano-hybrid composite specimens were prepared using a Teflon mold. The specimens' surfaces were prepared according to the following groups: group 1, no modeling agent; group 2, Modeling Liquid; group 3, a universal adhesive (G-Premio Bond); and group 4, the first step of a 2-step self-adhesive system (OptiBond XTR). Specimens were randomly allocated into 2 groups (n = 8) according to the storage medium (distilled water or coffee). VHN, Ra, and ΔE were measured at 24 hours, 1 week, and 6 weeks. The Kruskal-Wallis test followed by the Bonferroni correction for pairwise comparisons was used for statistical analysis (α = 0.05). Results: Storage time did not influence the VHN of the nano-hybrid composite in any group (p > 0.05). OptiBond XTR Primer application affected the VHN negatively in all investigated storage medium and time conditions (p < 0.05). Modeling Liquid application yielded improved Ra values for the specimens stored in coffee at each time point (p < 0.05). Modeling Liquid application was associated with the lowest ΔE values in all investigated storage medium and time conditions (p < 0.05). Conclusion: Different types of modeling agents could affect the surface properties and discoloration of nano-hybrid composites.

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.4
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• pp.33-43
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• 2013

That occur in the ocean and the efficient management of marine litter on marine pollution oil spill response one step further strategies are needed. Marine pollution accidents occurred in 2011, a total of 287 and was found in runoff 369 kL, respectively compared to the previous year decreased by 13% and 39%. Average amount of marine materials during 5-years represent the oil flow of 310.5 kL (heavy fuel oil of 106.0 kL, diesel of 178.9 kL, oily bilge water of 22.3 kL, other oil of 7.7 kL) and the waste of 62.3 tons, the hazardous and noxious substances (HNS) was 510.6 kL. Marine emissions in 2011 by type of waste that a total amount of dumping 3,972 $m^3$, and livestock manure 795 $m^3$(20%), waste water 1,431 $m^3$(36%), sewage sludge 887 $m^3$(22%), wastewater sludge, 813 $m^3$(21%), manure 5 $m^3$(0.1%), other 41 $m^3$(0.9%), respectively. The concept of marine waste and needs to be more clearly defined. Integrated management of hazardous chemicals according to the incident management system should be established. To remove of coastal pollution, response officer needs korean coast response system. Like the marine pollution response, coastal pollution response systems also require step response.