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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Naval Architecture and Ocean Engineering
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Journal DOI :
The Society of Naval Architects of Korea
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Volume & Issues
Volume 5, Issue 4 - Dec 2013
Volume 5, Issue 3 - Sep 2013
Volume 5, Issue 2 - Jun 2013
Volume 5, Issue 1 - Mar 2013
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Static and dynamic mooring analysis - Stability of floating production storage and offloading (FPSO) risers for extreme environmental conditions
Rho, Yu-Ho ; Kim, Kookhyun ; Jo, Chul-Hee ; Kim, Do-Youb ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 179~187
DOI : 10.3744/JNAOE.2013.5.2.179
Floating production storage and offloading (FPSO) facilities are used at most of the offshore oil fields worldwide. FPSO usage is expected to grow as oil fields move to deeper water, thus requiring the reliability and stability of mooring wires and risers in extreme environmental conditions. Except for the case of predictable attack angles of external loadings, FPSO facilities with turret single point mooring (SPM) systems are in general use. There are two types of turret systems: permanent systems and disconnectable turret mooring systems. Extreme environment criteria for permanent moorings are usually based on a 100-year return period event. It is common to use two or three environments including the 100-year wave with associated wind and current, and the 100-year wind with associated waves and current. When fitted with a disconnectable turret mooring system, FPSOs can be used in areas where it is desirable to remove the production unit from the field temporarily to prevent exposure to extreme events such as cyclones or large icebergs. Static and dynamic mooring analyses were performed to evaluate the stability of a spider buoy after disconnection from a turret during cyclone environmental conditions.
A method of inferring collision ratio based on maneuverability of own ship under critical collision conditions
You, Youngjun ; Rhee, Key-Pyo ; Ahn, Kyoungsoo ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 188~198
DOI : 10.3744/JNAOE.2013.5.2.188
In constructing a collision avoidance system, it is important to determine the time for starting collision avoidance maneuver. Many researchers have attempted to formulate various indices by applying a range of techniques. Among these indices, collision risk obtained by combining Distance to the Closest Point of Approach (DCPA) and Time to the Closest Point of Approach (TCPA) information with fuzzy theory is mostly used. However, the collision risk has a limit, in that membership functions of DCPA and TCPA are empirically determined. In addition, the collision risk is not able to consider several critical collision conditions where the target ship fails to take appropriate actions. It is therefore necessary to design a new concept based on logical approaches. In this paper, a collision ratio is proposed, which is the expected ratio of unavoidable paths to total paths under suitably characterized operation conditions. Total paths are determined by considering categories such as action space and methodology of avoidance. The International Regulations for Preventing Collisions at Sea (1972) and collision avoidance rules (2001) are considered to solve the slower ship's dilemma. Different methods which are based on a constant speed model and simulated speed model are used to calculate the relative positions between own ship and target ship. In the simulated speed model, fuzzy control is applied to determination of command rudder angle. At various encounter situations, the time histories of the collision ratio based on the simulated speed model are compared with those based on the constant speed model.
Model test of new floating offshore wind turbine platforms
Shin, Hyunkyoung ; Pham, Thanh Dam ; Jung, Kwang Jin ; Song, Jinseob ; Rim, Chaewhan ; Chung, Taeyoung ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 199~209
DOI : 10.3744/JNAOE.2013.5.2.199
This paper presents the model test results of 3 new spar platforms which were developed based on the OC3-Hywind spar to support a 5-MW wind turbine. By changing the shape but keeping both volume and mass of OC3-Hywind spar platform, those platforms were expected to experience different hydrodynamic and hydrostatic loads. The scale models were built with a 1/128 scale ratio. The model tests were carried out in waves, including both rotating rotor effect and mean wind speed. The characteristic motions of the 3 new models were measured; Response Amplitude Operators (RAO) and significant motions were calculated and compared with those of OC3-Hywind.
Simulation of optimal arctic routes using a numerical sea ice model based on an ice-coupled ocean circulation method
Nam, Jong-Ho ; Park, Inha ; Lee, Ho Jin ; Kwon, Mi Ok ; Choi, Kyungsik ; Seo, Young-Kyo ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 210~226
DOI : 10.3744/JNAOE.2013.5.2.210
Ever since the Arctic region has opened its mysterious passage to mankind, continuous attempts to take advantage of its fastest route across the region has been made. The Arctic region is still covered by thick ice and thus finding a feasible navigating route is essential for an economical voyage. To find the optimal route, it is necessary to establish an efficient transit model that enables us to simulate every possible route in advance. In this work, an enhanced algorithm to determine the optimal route in the Arctic region is introduced. A transit model based on the simulated sea ice and environmental data numerically modeled in the Arctic is developed. By integrating the simulated data into a transit model, further applications such as route simulation, cost estimation or hindcast can be easily performed. An interactive simulation system that determines the optimal Arctic route using the transit model is developed. The simulation of optimal routes is carried out and the validity of the results is discussed.
Rapid response calculation of LNG cargo containment system under sloshing load using wavelet transformation
Kim, Yooil ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 227~245
DOI : 10.3744/JNAOE.2013.5.2.227
Reliable strength assessment of the Liquefied Natural Gas (LNG) cargo containment system under the sloshing impact load is very difficult task due to the complexity of the physics involved in, both in terms of the hydrodynamics and structural mechanics. Out of all those complexities, the proper selection of the design sloshing load which is applied to the structural model of the LNG cargo containment system, is one of the most challenging one due to its inherent randomness as well as the statistical analysis which is tightly linked to the design sloshing load selection. In this study, the response based strength assessment procedure of LNG cargo containment system has been developed and proposed as an alternative design methodology. Sloshing pressure time history, measured from the model test, is decomposed into wavelet basis function targeting the minimization of the number of the basis function together with the maximization of the numerical efficiency. Then the response of the structure is obtained using the finite element method under each wavelet basis function of different scale. Finally, the response of the structure under entire sloshing impact time history is rapidly calculated by synthesizing the structural response under wavelet basis function. Through this analysis, more realistic response of the system under sloshing impact pressure can be obtained without missing the details of pressure time history such as rising pattern, oscillation due to air entrapment and decay pattern and so on. The strength assessment of the cargo containment system is then performed based on the statistical analysis of the stress peaks selected out of the obtained stress time history.
Determination of an economical shipping route considering the effects of sea state for lower fuel consumption
Roh, Myung-Il ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 246~262
DOI : 10.3744/JNAOE.2013.5.2.246
With increases in international oil prices, the proportion of fuel cost to the operational costs of a ship is currently increasing. To reduce fuel cost, a method for determining an economical route for a ship based on the acquisition of the sea state and the estimation of fuel consumption is proposed. The proposed method consists of three items. The first item is to acquire the sea state information in real time. The second item is to estimate the fuel consumption of a ship according to the sea state. The last item is to find an economical route for minimal fuel consumption based on the previous two items. To evaluate the applicability of the proposed method, it was applied to routing problems in various ocean areas. The result shows that the proposed method can yield economical ship routes that minimize fuel consumption. The results of this study can contribute to energy savings for environmentally friendly ships.
Fluid-structure interaction analysis of deformation of sail of 30-foot yacht
Bak, Sera ; Yoo, Jaehoon ; Song, Chang Yong ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 263~276
DOI : 10.3744/JNAOE.2013.5.2.263
Most yacht sails are made of thin fabric, and they have a cambered shape to generate lift force; however, their shape can be easily deformed by wind pressure. Deformation of the sail shape changes the flow characteristics over the sail, which in turn further deforms the sail shape. Therefore, fluid-structure interaction (FSI) analysis is applied for the precise evaluation or optimization of the sail design. In this study, fluid flow analyses are performed for the main sail of a 30-foot yacht, and the results are applied to loading conditions for structural analyses. By applying the supporting forces from the rig, such as the mast and boom-end outhaul, as boundary conditions for structural analysis, the deformed sail shape is identified. Both the flow analyses and the structural analyses are iteratively carried out for the deformed sail shape. A comparison of the flow characteristics and surface pressures over the deformed sail shape with those over the initial shape shows that a considerable difference exists between the two and that FSI analysis is suitable for application to sail design.
Investigation of bar parameters occurred by cross-shore sediment transport
Demirci, Mustafa ; Akoz, M. Sami ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 277~286
DOI : 10.3744/JNAOE.2013.5.2.277
Cross-shore sediment transport is very important factor in the design of coastal structures, and the beach profile is mainly affected by a number of parameters, such as wave height and period, beach slope, and the material properties of the bed. In this study cross-shore sediment movement was investigated using a physical model and various offshore bar geometric parameters were determined by the resultant erosion profile. The experiments on cross- shore sediment transport carried out in a laboratory wave channel for initial base slopes of 1/8, 1/10 and 1/15. Using the regular waves with different deep-water wave steepness generated by a pedal-type wave generator, the geometrical of sediment transport rate and considerable characteristics of beach profiles under storm conditions and bar parameters affecting on-off shore sediment transport are investigated for the beach materials with the medium diameter of
=0.25, 0.32, 0.45, 0.62 and 0.80 mm. Non-dimensional equations were obtained by using linear and non-linear regression methods through the experimental data and were compared with previously developed equations in the literature. The results have shown that the experimental data fitted well to the proposed equations with respect to the previously developed equations.
Numerical investigation of yaw angle effects on propulsive characteristics of podded propulsors
Shamsi, Reza ; Ghassemi, Hassan ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 287~301
DOI : 10.3744/JNAOE.2013.5.2.287
The present paper deals with the problems of yaw angle effects on podded propulsor performance. The study aims at providing insights on characteristics of podded propulsors in azimuthing condition. In this regard, a wide numerical simulation that concerned yaw angle effect measurement on podded propeller performance was performed. The Reynolds-Averaged Navier Stokes (RANS) based solver is used in order to study the variations of hydrodynamic characteristics of podded propulsor at various angles. At first, the propeller is analyzed in open water condition in absence of pod and strut. Next flow around pod and strut are simulated without effect of propellers. Finally, the whole unit is studied in zero yaw angle and azimuthing condition. Structured and unstructured mesh techniques are used for single propeller and podded propulsor. The performance curves of the propeller obtained by numerical method are compared and verified by the experimental results. The characteristic parameters including the torque and thrust of the propeller, the axial force and side force of unit are presented as function of velocity advance ratio and yaw angle. The results shows that the propeller thrust, torque and podded unit forces in azimuthing condition depend on velocity advance ratio and yaw angle.
Anti-slamming bulbous bow and tunnel stern applications on a novel Deep-V catamaran for improved performance
Atlar, Mehmet ; Seo, Kwangcheol ; Sampson, Roderick ; Danisman, Devrim Bulent ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 302~312
DOI : 10.3744/JNAOE.2013.5.2.302
While displacement type Deep-V mono hulls have superior seakeeping behaviour at speed, catamarans typically have modest behaviour in rough seas. It is therefore a logical progression to combine the superior seakeeping performance of a displacement type Deep-V mono-hull with the high-speed benefits of a catamaran to take the advantages of both hull forms. The displacement Deep-V catamaran concept was developed in Newcastle University and Newcastle University's own multi-purpose research vessel, which was launched in 2011, pushed the design envelope still further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. This paper presents the hullform development of this unique vessel to understand the contribution of the novel bow and stern features on the performance of the Deep-V catamaran. The study is also a further validation of the hull resistance by using advanced numerical analysis methods in conjunction with the model test. An assessment of the numerical predictions of the hull resistance is also made against physical model test results and shows a good agreement between them.
Experimental study on moonpool resonance of offshore floating structure
Yang, Seung-Ho ; Kwon, Sun-Hong ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 2, 2013, Pages 313~323
DOI : 10.3744/JNAOE.2013.5.2.313
Offshore floating structures have so-called moonpool in the centre area for the purpose of drilling, installation of subsea structures, recovery of Remotely-Operated Vehicle (ROV) and divers. However, this vertical opening has an effect on the operating performance of floating offshore structure in the vicinity of moonpool resonance frequency; piston mode and sloshing mode. Experimental study based on model test was carried out. Moonpool resonance of floating offshore structure on fixed condition and motion free condition were investigated. And, the effect of cofferdam which is representative inner structure inside moonpool was examined. Model test results showed that Molin's theoretical formula can predict moonpool resonance on fixed condition quite accurately. However, motion free condition has higher resonance frequency when it is compared with that of motion fixed. The installation of cofferdam moves resonance frequency to higher region and also generates secondary resonance at lower frequency. Furthermore, it was found that cofferdam was the cause of generating waves in the longitudinal direction when the vessel was in beam sea.