• Title/Summary/Keyword: 선수파

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An Analysis of the Hydroelastic Response of Large Floating Structures in Oblique Waves (사파중에 놓인 거대 부유체의 응답에 대한 유탄성 해석)

  • In-H. Sim;Jae-D. Yoon;Hang-S. Choi
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.3
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    • pp.83-92
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    • 1999
  • In this paper, the fluid-structure interaction of large floating structures has been rigorously analyzed and the shear effect on the structural deformation has been investigated in oblique waves. A constant panel method(CPM) based on the Green function method is implemented for computing the hydrodynamic pressure, while a finite element method(FEM) is applied for the structural response based on the Mindlin plate theory with including shear deformation. In order to validate the method, we compared numerical results with experimental ones of Mega Float carried out by Yago & Endo in head waves. General behavior shows good agreement but the local displacement at the ends is slightly different. The numerical results show that the radiation pressure due to the fluid-structure interaction is locally larger than that of wave excitation and mooring devices greatly reduce the response. It is observed that the shear effects among the total deformation constitutes about 4% in the case of Mega Float in oblique waves.

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Computational and Experimental Studies on Added Resistance of AFRAMAX-Class Tankers in Head Seas (선수파 중 AFRAMAX급 유조선의 부가저항에 대한 실험과 수치계산)

  • Oh, Seunghoon;Yang, Jinho;Park, Sang-Hun
    • Journal of the Society of Naval Architects of Korea
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    • v.52 no.6
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    • pp.471-477
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    • 2015
  • When a ship sails in a seaway, the resistance on a ship increases due to incident waves and winds. The magnitude of added resistance amounts to about 15–30% of a calm-water resistance. An accurate prediction of added resistance in waves, therefore, is essential to evaluate the performance of a ship in a real sea state and to design an optimum hull form from the viewpoint of the International Maritime Organization (IMO) regulations such as Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI). The present study considers added resistance problem of AFRAMAX-class tankers with the conventional bow and Ax-bow shapes. Added resistance due to waves is successfully calculated using 1) a three-dimensional time-domain seakeeping computations based on a Rankine panel method (three-dimensional panel) and 2) a commercial CFD program (STAR-CCM+). In the hydrodynamic computations of a three-dimensional panel method, geometric nonlinearity is accounted for in Froude-Krylov and restoring forces using simple wave corrections over exact wet hull surface of the tankers. Furthermore, a CFD program is applied by performing fully nonlinear computation without using an analytical formula for added resistance or empirical values for the viscous effect. Numerical computations are validated through four degree-of-freedom model-scale seakeeping experiments in regular head waves at the deep towing tank of Hyundai Heavy Industries.

A Study on the Bow Hull Form Design of Full Ship Considering the Nonlinear Waves (비선형파를 고려한 비대선의 선수선형설계에 관한 연구)

  • Yu, Jin-Won;Lee, Young-Gill;Choi, Si-Young;Choi, Young-Chan;Jeong, Kwang-Leol;Ha, Yoon-Jin
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.5
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    • pp.671-679
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    • 2010
  • This paper introduces a new hull form design method for the bow of a full ship, by actively applying the relation between the fore-body hull form and its wave resistance characteristics. For the hull form design, the Series 60($C_B=0.8$) hull is chosen as the parent ship, and Kracht's charts are used to determine the parameters of the bulbous bow in the early stages of hull form design. Several hull forms have been tested in order to obtain enough hull form variations with various bow shapes and design parameters in the search of the best design. In order to investigate the resistance characteristics of the designed hull forms, numerical simulations with corresponding model tests have been rigorously performed. For the numerical simulations, the Marker-density method is employed to track the nonlinear phenomena of the free surface(program IUBW). Model tests have also been performed to achieve an improved research performance using the designed hulls. Both numerical and experimental results show that the wave resistance of the hull forms can be effectively diminished if the bows are designed using the method introduced in this research. It is also expected that this research can facilitate better productivity in hull form design, especially at the preliminary design stage of a full ship type vessel.

Roll Damping Moment of a Small Fishing Vessel by Free Rolling Test in Waves (파랑중 자유 횡동요 시험에 의한 소형어선의 횡동요 감쇠모멘트에 관한 연구)

  • H.H. Chun;S.H. Chun;S.Y. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.37 no.2
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    • pp.30-37
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    • 2000
  • The roll damping characteristics of the three models of a 3ton class fishing vessel, that is the bare hull, hull with bilge keels, and hull with bilge keels and a central wing are investigated by the free roll tests in head waves in a towing tank with the variations of the forward speed, initial angle and OG. The wave length variations are also included. The experimental results are compared with the numerical results of mathematical modellings by the energy method for these three models and the energy dissipation patterns are also compared. The roll damping speed increases, the effect of the waves on the roll damping of the models with the additional devices is negligible due to the much increased damping caused by the lift increase.

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An Experimental Study on the Resistance Performance of Small Size Fishing Vessel (소형 연안어선의 저항성능에 관한 실험적 연구)

  • Kim, Do-Jung;Park, Je-Woong;Kim, Ju-Nam;Jeong, Uh-Cheul
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.40 no.4
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    • pp.304-310
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    • 2004
  • Resistance performance of small size fishing vessel is experimentally investigated to find out the effect of fore-body shape and trim for the better hull from development. The tests are performed for five different cases in the high speed circulating water channel(CWC). Wave patterns are observed to investigate the relation between the resistance performance and the wave characteristics.

Experimental Study of Motion Behavior of Side-by-Side Moored Two Floating Bodies Including Sloshing in Head Sea (선수파 중 슬로싱을 고려한 병렬배치된 두 부유체의 거동 특성에 관한 실험 연구)

  • Cho, Seok-Kyu;Sung, Hong-Gun;Hong, Jang-Pyo;Hong, Sa-Young;Hong, Seok-Won
    • Journal of Ocean Engineering and Technology
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    • v.26 no.6
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    • pp.46-52
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    • 2012
  • The motions and drift forces of side-by-side moored FSRU and LNGC including the sloshing effect, were studied using experiments. The FSRU and LNGC contained LNG cargo tanks and the LNG sloshing could affect the motions and drift forces of the structures due to its coupling with floating body motion. The effect of coupling can vary with the LNG filling level, and the effect of the filling level was investigated. The coupling effect was stronger at lower filling level. It was confirmed that longitudinal sloshing influenced the surge and surge mean drift force in head sea. In addition, gap flow affected the sway and mean drift forces. Sloshing attenuated the sway and yaw excited by gap flow in side-by-side configuration.

Effects of Wall Boundary Condition on Velocity Distribution of Shallow Water Flow (벽면경계조건이 천수흐름 유속분포에 미치는 영향)

  • Seo, Il-Won;Song, Chang-Geun
    • Proceedings of the Korea Water Resources Association Conference
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    • 2010.05a
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    • pp.189-193
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    • 2010
  • RMA-2, Telemac-2D, River2D 등 기존의 대부분 국내외 상용모형에서는 내부 경계인 하천구조물과 외부 경계인 측벽에서의 경계조건을 활동조건(slip condition)으로 가정하여 흐름장을 계산하였다. 그러나 실제로 벽면에서는 마찰력에 의해 흐름이 존재하지 않는 무활조건(no slip condition)이 물리적으로 타당하다. 따라서 본 연구에서는 내부구조물인 교각이 존재하는 영역에서의 수평 2차원 유속분포를 구하기 위해 천수방정식을 Galerkin법과 Newton-Raphson법에 의해 이산화한 수치모형을 개발하였다. Yulistiyanto 등(1998)이 수치모의 및 수리실험에 사용한 조건을 채택하여 벽면에서의 접선방향 유속이 존재하는 활동조건과 벽면에서 유속이 없는 무활조건을 부여하고 교각을 포함한 수로에서 유속, 수위 및 전단분포를 해석하였다. 활동경계조건을 적용한 경우 교각 표면을 따라 큰 유속이 분포하고 후면에서도 관성력에 의해 흐름방향 유속이 두드러지게 나타났으나 무활조건을 적용한 경우 교각 후면에서 와가 형성되고 후류현상이 두드러지게 나타났다. 무활조건을 적용한 경우 교각 전면부에서는 선수파(bow wave)가 4 cm정도 높게 나타났으며 교각 측면부에서는 2 cm 높게 나타났다. 반면 교각 후면에서는 후류의 영향으로 수면이 2 cm 낮게 분포하였다. 교각부에 작용하는 전단력을 분석한 결과 무활조건을 적용한 경우가 활동조건을 적용한 경우에 비해 최대 6배 높은 전단력이 나타났다.

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An Experimental Study on the Effects of Bow Flare Angle about Green Water in Regular Waves (규칙파 중 갑판침입수에 미치는 선수 플레어 각도의 영향에 관한 실험적 연구)

  • Ha, Yoon-Jin;Lee, Young-Gill;Jeong, Kwang-Leol
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.1
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    • pp.79-86
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    • 2012
  • It is very important to investigate and understand the motion of a FPSO on waves because green water phenomenon occurs owing to the relative motions between incident waves and a ship on them. In this research, both experimental and some numerical approaches have been performed in head sea conditions with regular waves. As an object model of this research, a FPSO model is set free to heave and pitch during the experiments. Also, the motions of the FPSO model which are the results of the experiments are used for the corresponding numerical computations. The purpose of this study is to clarify the effect of bow flare on green water load. In this research, it is found that the amount of green water entered from the side of bow is decreased by the increase of bow flare angle. Moreover, the relation between the green water on the bow upper deck and the impact load on the vertical wall located at turrethead is investigated. The results of this research could be used as one of the fundamental data to design bow flares. Also, an optimized bow flare angle is proposed in this study.

The Evaluation of Hydrodynamic Resistance and Motion Response Characteristics of Platform Supply Vessel (해양플랜트지원선의 저항성능과 운동응답특성에 관한 연구)

  • Seo, Kwang-Cheol;Gim, Ok-Sok;Ryu, Youn-Chul;Atlar, Mehmt;Lee, Gyoung-Woo
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.19 no.4
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    • pp.397-402
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    • 2013
  • In this study, numerical hull form development of a platform supply vessel, a full scale with the overall length of 26.75m, was performed to predict a bare-hull resistance and a large scale of model tests with a 1/10 scaled model were conducted to verify the success of numerical results. Numerical analysis on heave and pitch motion as a function of encounter frequency and ship's speed for the prediction of seakeeping characteristics are also presented. The experiment results of resistance agreed well with numerical analysis. As a result in the motion response characteristics, the heave RAO indicates high values with the range of encounter frequency 1.8~2.0. The Pitch RAO indicates high motion response characteristics at Beaufort scale No. 3 and 4 in rough seas.

Experimental Study on the Deck Wetting of a Container Ship in Irregular Head Waves (콘테이너선의 불규칙파중 갑판침수에 관한 실험적 고찰)

  • Sa-Young,Hong;Pan-Mook,Lee;Do-Sig,Gong
    • Bulletin of the Society of Naval Architects of Korea
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    • v.27 no.2
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    • pp.31-39
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    • 1990
  • Deck wetness phonomena has long been considered as one of the factors that degrade the performance of a ship in waves. In rough weather, the frequent shipping of water may give rise to the capsizing of the ship. Therefore an appropriate above water bow design is an improtant assert to a ship of which successful performance in rough weather is a prerequisite such as a warship. In this paper the experimental technique for estimation of deck wetness frequency is presented. The results of the model tests are compared with those of calculation using Ochi's formula. Finally the applicability of Ochi's formula is discussed.

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