• Journal of the Society of Naval Architects of Korea
• /
• v.32 no.3
• /
• pp.37-43
• /
• 1995

The procedure and the results of the full scale strain measurement of the long-range high-speed foil catamaran are described. The wave induced stresses at the center struts of the foils were measured during the sea trials in order to evaluate the hydrodynamic force acting on the foils and to verify the structural safety of the foil structures. From the statistical properties of the measured response of the stress, the most probable maximum values of the lift force and the stresses at the foils in service life of the ship are predicted and compared with the design parameters of the foils which were applied in the design of the subject ship. The available prediction processes of the measured stress are studied and the results of the applied processes are compared with each other.

• Journal of the Society of Naval Architects of Korea
• /
• v.30 no.4
• /
• pp.31-38
• /
• 1993

Horn rudders or flap rudders with a gap between forward and after part are used for effective steering of a ship or a submerged body. It is necessary to analyze the effect of a gap since it affects the performance of rudders. In this paper, an equation to calculate the lift acting on a two-dimensional flap rudder in uniform flow is derived by using the thin hydrofoil theory and the analytic solution of viscous flow in a channel formed by two coaxial cylindrical walls to which a pressure gradient is applied.

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

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.1
• /
• pp.1-10
• /
• 1997

Viscous flow around actual ship is calculated by an use of RANS equations. The propriety of this computing method, usefulness to hull form design and the scale effect which is the effect of viscous flow depending on the scale of ship model are investigated. Reynolds stress is modelled by using k-${\varepsilon}$ turbulence model and the law of wall is applied near the body. Body fitted coordinates are introduced for the treatment of the arbitrary 3-dimensional shape of the ship hull form. The transformed equations in the computational domain are numerically solved by an employment of FVM. In the calculation of pressure, SIMPLE method is adopted and the solution of the discretized equation is obtained by the line-by-line method with the use of TDMA The calculations of two ships, 4410 TEU container carrier and 50,000 DWT class bulk carrier, are performed at model and actual ship scale. The results are compared and discussed with the model test results which are viscous resistance, nominal wake distribution at propeller plane and limiting streamline on the hull surface. They describe the effect of stem form and the scale effect very well. In particular, the calculated nominal wake distribution and limiting streamline are agreed qualitatively with the experiments and the viscous resistance values are estimated within ${\pm}5%$ difference from the resistance tests.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.4
• /
• pp.620-631
• /
• 2022

This paper shows the numerical prediction of the change in oil outflow rate according to the orifice shape of a damaged ship by using the computational fluid dynamics (CFD) analysis method. It also provides discharge coefficients for various orifice shapes to be used in theoretical prediction approaches. The oil outflow from the model ship was analyzed using a multiphase flow method under the condition that the Froude and Reynolds number similitudes were satisfied. The present numerical results were verified by comparing them with the available experimental data. Along with the aspect ratio of the orifice and the wall thickness of the cargo tank, the effects of the orifice shapes defined by mathematical figures on the oil outflow were investigated. To consider more realistic situations, the investigation of the ef ect of the crushed iron plate around the damaged part was also included. The numerical results confirmed the change in oil outflow time for various shapes of the damaged part of the oil tank, and discharge coefficients that quantify the viscous effects of those orifice shapes were extracted. To verify the predicted discharge coefficients, they were applied to an oil spill estimation equation. As a result, a good agreement between the CFD and theoretical results was obtained.

• Journal of Korea Port Economic Association
• /
• v.36 no.4
• /
• pp.17-30
• /
• 2020

In the shipping industry, it is essential to engage in the preemptive prediction of freight rate volatility through market monitoring. Considering that freight rates have already started to fall, the loss of shipping companies will soon be uncontrollable. Therefore, in this study, factors affecting the freight rates of bulk carriers, which have relatively large freight rate volatility as compared to container freight rates, were quantified and analyzed. In doing so, we intended to contribute to future shipping market monitoring. We performed an analysis using a vector error correction model and estimated the influence of six independent variables on the charter rates of bulk carriers by Handy Size, Supramax, Panamax, and Cape Size. The six independent variables included the bulk carrier fleet volume, iron ore traffic volume, ribo interest rate, bunker oil price, and Euro-Dollar exchange rate. The dependent variables were handy size (32,000 DWT) spot charter rates, Supramax 6 T/C average charter rates, Pana Max (75,000 DWT) spot charter, and Cape Size (170,000 DWT) spot charter. The study examined charter rates by size of bulk carriers, which was different from studies on existing specific types of ships or fares in oil tankers and chemical carriers other than bulk carriers. Findings revealed that influencing factors differed for each ship size. The Libo interest rate had a significant effect on all four ship types, and the iron ore traffic volume had a significant effect on three ship types. The Ribo rate showed a negative (-) relationship with Handy Size, Supramax, Panamax, and Cape Size. Iron ore traffic influenced three types of linearity, except for Panamax. The size of shipping companies differed depending on their characteristics. These findings are expected to contribute to the establishment of a management strategy for shipping companies by analyzing the factors influencing changes in the freight rates of charterers, which have a profound effect on the management performance of shipping companies.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.2
• /
• pp.244-253
• /
• 2022

Recently, installation projects of structures such as offshore wind farms have been increasing, and the installation of such marine obstacles could affect ships that pass nearby. Therefore, the purpose of this study was to quantitatively evaluate the risk posed to passing ships due to obstacles in their passage. Hence, parameters that affected the risk were selected, and scenarios were set based on the parameters. The scenarios were evaluated through the ES model, which is a risk assessment model, and we confirmed that the risk ratio increased as the size of the obstacle increased, the safe distance from the obstacle increased, the speed of ship decreased, and the traffic volume increased. Additionally, we found that when the traffic flow direction was designated, the risk ratio was lower than that of general traffic flow. In this study, we proposed a generalization model based on the results of the performed scenarios, applied it to the Dadaepo offshore wind farm, and demonstrated that the estimation of the approximate risk ratio was possible through the generalization model. Finally, we judged that the generalization model proposed in this study could be used as a preliminary reference for the installation of marine obstacles.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.4
• /
• pp.433-440
• /
• 2019

Offshore working environments such as ships, offshore oil and gas plants, and offshore wind turbines are isolated and directly exposed to rough seas, which pose high risks of safety accidents. Therefore, all workers in offshore plants should be able to cope with emergency situations and must be qualified according to relevant laws and regulations such as the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW Convention) and Offshore Petroleum Industry Training Organization (OPITO) standards. In particular, marine workers should be able to perform cardiopulmonary resuscitation (CPR) in isolated locations or enclosed and confined spaces such as those in life-boats, life-rafts, rescue-boats, etc. Because the floor material is made of rubber, it may be difficult to perform chest compressions in life-rafts used to escape from emergency situations in ships or offshore plants. Chest compressions performed on life-rafts may reduce the accuracy of CPR and increase fatigue for those providing aid. To measure the accuracy and fatigue of those performing CPR in life-rafts, 15 experimenters with more than five years of experience as first aid instructors were exposed to different CPR environments in a marine safety training center equipped with an artificial wave generator. The results showed that the accuracy of CPR in the classroom was 99.6 %, but that in various life-raft environments was only 84 %. T-verification of the two sites confirmed the reduced accuracy of CPR performed on life-rafts. CPR on life-rafts should be performed in groups of two and with the use of automated chest compression devices.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.25 no.4
• /
• pp.69-80
• /
• 1988

This paper proposes simple formulae for buckling and ultimate strength estimation of plates subjected to water pressure and uniaxial compression. For the construction of a formula for elastic buckling strength estimation, parametric study for actual ship plates with varying aspect ratios and the magnitude of water pressure is carried out by means of principle of minimum potential energy. Based on the results by parametric study, a new formula is approximately expressed as a continuous function of loads and aspect ratio. On the other hand, in order to get a formula for ultimate strength estimation, in-plane stress distribution of plates is investigated through large deflection analysis and total in-plane stresses are expressed as an explicit form. By applying Mises's plasticity condition, ultimate strength criterion is then derives. In the case of plates under relatively small water pressure, the results by the proposed formulae are in good agreement compared with those by other methods and experiment. But present formula overestimates the ultimate strength in the range of large water pressure. However, actual ship plates are subjected to relatively small water pressure except for the impact load due to slamming etc.. Therefore, it is considered that present formulae can be applied for the practical use.

• Korean Journal of Heritage: History & Science
• /
• v.55 no.4
• /
• pp.6-22
• /
• 2022

In this paper classifies the types of 228 anchor stones discharged from the west and south coasts, assumes a combined method by type, routes through discharge locations, and It attempted to estimate the burial site. Prior to classification of types, the weight, thickness, width, and length of the anchor stone were measured, and the largest Young in the tomb The scent weight was classified into I~V groups, and the shape of the anchor stone was classified into 1-6 types. All of these weight and shape correlations It was classified into 17 types. The combined method by type is 180kg or less depending on the morphological characteristics of the reference value of the extracted anchor stone, and the type An anchor of type 1 or 2 is used in combination with an anchor, and a anchor of type 3 or 6 weighs more than 180kg and is combined with an anchor The dragon was assumed to be an anchor. Along with this, the route and burial site are identified through past records and testimony of local residents It was checked against the data. The route was largely consistent with past records, but the new route was apparent in waters near the island or inland It was also drawn. In the case of burial sites, small and large in Taean Mado Sea and Jindo Byeokpajin Sea, where anchor stones are concentrated, Considering the pattern of the type anchor stones being discharged, it was consistent with the testimony that ships of various sizes were mysterious in the two seas. Based on this type classification, a study on the spatiality of the anchors was conducted. First, a comparison and analysis was done on whether actual real data, such as anchor stones, old ships, and relics, were identified on the Joun-ro route and international trade routes as recorded in the past literature. Where there was no record, the route was estimated based on real data. To this end, routes estimated based on the testimony of local residents and modern ship workers were analyzed as to whether ships traveled there in the past and whether they could actually sail. Next, the location of each seedling was estimated by ship size according to the weight of the anchor stone. In the case of the Taean Mado Sea and Jindo Byeokpajin Sea, both small and large anchor stones were discharged from the coastline and were far away.