• Title, Summary, Keyword: 횡동요

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Simulation of Vessel Motion Control by Anti-Rolling Tank (능동형 횡동요 저감 장치를 이용한 선박운동제어 시뮬레이션)

  • Kim, Kyung Sung;Lee, Byung-Hyuk
    • Journal of Ocean Engineering and Technology
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    • v.32 no.6
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    • pp.440-446
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    • 2018
  • The effects of an anti-rolling tank (ART) on vessel motions were numerically investigated. The potential-based BEM vessel motion simulation program and particle-based computational fluid dynamics program were dynamically coupled and used to perform a simulation of vessel motions with ART. From the time domain simulation results, the response amplitude operators for sway and roll motions were obtained and compared with the corresponding experimental and numerical results. Because the main purpose of ART was only to reduce roll motions, it was important to show that the natural properties of a floating vessel were not changed by the effects of ART. Various ART filling ratios and several ART positions were considered. In conclusion, ART only reduced the roll motion regardless of its filling ratio and position.

A Study on Conceptual Design of Anti-rolling Devices for 250 TEU Class Mobile Harbors (250 TEU급 모바일하버를 위한 횡동요 저감 장치의 개념 설계 연구)

  • Chung, T.Y.;Moon, S.J.;Lew,, J.M.;Park, C.H.;Cho, H.W.;Kim, B.I.;Yoon, H.K.;Kang, J.Y.
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.7
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    • pp.629-636
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    • 2010
  • A Mobile Harbor is a new transportation platform which can load and unload has containers to and from very large container ships on the sea. Currently designed Mobile Harbor a catamaran type which is equipped with precisely controlled gantry crane on the deck, and can transport 250 TEUs at a time. Loading and unloading works by crane require very small motion of Mobile Harbor in waves, because it may be operated outside of harbors. In this project, applicability of both tuned-type anti-rolling tank and maglev-type active mass driver is studied as anti-rolling systems.

Study on Numerical Sensitivity and Uncertainty in the Analysis of Parametric Roll (파라메트릭 횡동요 수치해석의 민감도 및 불확실성에 대한 연구)

  • Park, Dong-Min;Kim, Tae-Young;Kim, Yong-Hwan
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.1
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    • pp.60-67
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    • 2012
  • This study considers the numerical analysis on parametric roll for container ships. As a method of numerical simulation, an impulse-response-function approach is applied in time domain. A systematic study is carried out for the parametric roll of two container ships, particularly observing the sensitivity of computational results to some parameters which can affect the analysis of parametric roll. The parameters to be considered are metacentric height (GM), simulation time window, and the discretization of wave spectrum. Based on the result of parametric roll simulation, numerical sensitivity and uncertainty in computational analysis are discussed.

Development of a Stability System to prevent a Capsize of a Small Fishing Vessel (소형어선의 전복방지화 안정장치 시스템 개발에 관한 연구)

  • Cheon, Seung-Hyeon;Jeon, Ho-Hwan;Kim, Chang-Hun;Kim, Si-Yeong;,
    • Journal of Ocean Engineering and Technology
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    • v.13 no.1
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    • pp.130-137
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    • 1999
  • The wing-flap stabilizing system attached under the hull bottom of a small fishing vessel to prevent the capsize by controlling the roll motions has been developed. This paper describes the background of the system design together with the experimental results. The effectiveness of the system is proven by the towing tank tests with a 1/4 scale model, showing that the roll motions of the model are much reduced by the active flap control in multidirectional irregular waves forward speeds.

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A Sea-Trial Test of a Pendulum-type Mass Driving Anti-Rolling System for Small Ships (소형 선박용 진자식 횡동요 저감장치의 실선시험)

  • 문석준;박찬일;정종안;김병인;윤현규
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.438-441
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    • 2004
  • Reduction of a ship's rolling is the most important performance requirement for improving the safety of the crew on board and preventing damage to cargos as well as improving the comfort of the ride. A mass driving anti-rolling system (MD-ARS) might be one candidate of several systems against the ship's rolling. In this paper, a sea-trial test on a pendulum-type MD-ARS passively operated is carried out in Suyoung, Busan. After the system is installed on the cabin of the small leisure boat, a series of test is conducted before and after operating the system. Through the test, it is confirmed that the roll rate of the ship is pretty well reduced by the system.

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Estimation of Roll Related Coefficients of a Ship by Using the System Identification Method (시스템 식별법을 이용한 선박의 횡동요 계수 추정)

  • 윤현규;손남선
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.4
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    • pp.53-58
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    • 2004
  • When a fast container ship or a naval vessel is turning, comparable roll motions occur. Therefore, roll effect has to be considered in the horizontal equations of motion of the ship to predict the maneuverability well. In this thesis, a new method to determine a roll model structure and estimate its coefficients by applying the system identification technique to the data of sea trial tests was proposed. The simulation results from the estimated roll model were well consistent with the true one in spite of the difference between the estimated and the true model structures of roll hydrodynamic moment.

Study on Roll Motion Characteristics of a Rectangular Floating Structure in Regular Waves (규칙파 중 사각형 부유식 구조물의 횡동요 운동특성에 대한 연구)

  • Kim, Min-Gyu;Jung, Kwang-Hyo;Park, Sung-Boo;Lee, Gang-Nam;Park, Il-Ryong;Suh, Sung-Bu
    • Journal of Ocean Engineering and Technology
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    • v.33 no.2
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    • pp.131-138
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    • 2019
  • This study focused on the roll motion characteristics of a two-dimensional (2D) rectangular floating structure under regular beam sea conditions. An experiment was conducted in a 2D wave tank for a roll free decay test in calm water and the roll motion in a range of regular waves with and without heave motion to investigate the motion response and heave influence on the roll motion. A numerical study was carried out using Reynolds-averaged Navier Stokes (RANS)-based CFD simulations. A grid convergence test was conducted to accurately capture the wave condition on the free surface based on the overset mesh and wave forcing method. It was found in the roll free decay test that the numerical results agreed well with the experimental results for the natural roll period and roll damping coefficient. It was also observed that the heave motion had an impact on the roll motion, and the responses of the heave and roll motion from the CFD simulations were in reasonable agreement with those from the experiment.

Experimental Study on Estimation of Roll Damping for Various Midship Sections (중앙 단면 형상에 따른 횡동요 감쇠 추정 실험 연구)

  • Park, Byeongwon;Jung, Dong Woo;Jung, Jaesag;Park, Inbo;Cho, Seok-Kyu;Sung, Hong Gun
    • Journal of Ocean Engineering and Technology
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    • v.33 no.4
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    • pp.322-329
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    • 2019
  • The magnitude of the roll motion of a floating structure depends on the roll damping acting on the body. In other words, the roll damping of a floating structure must be accurately obtained in order to precisely evaluate the roll motion. Various methods are used to evaluate the roll damping of a floating structure, such as the linear potential theory, computational fluid dynamics (CFD), and model tests. However, it is difficult to evaluate the roll motion of a floating structure with appendages such as a bilge keel and riser slot due to the limitation of ignoring the viscous effects in the linear potential theory. Among these methods, a model test based on a free decay test and harmonic excited roll motion (HERM) is known to be the most reliable method to estimate the roll damping of the floating structures. In this study, model tests using free decay and HERM techniques were performed in the Ocean Engineering Basin (OEB) of KRISO with various types of midship sections. The roll damping results were estimated based on post-processing methods using both techniques, and the roll damping results were compared.

Experimental Study on Free Roll Decay Motions of a Damaged Ship for CFD Validation Database (CFD 검증용 데이터베이스 구축을 위한 손상 선박의 횡동요 감쇠 운동에 대한 실험적 연구)

  • Lee, Sung-Kyun;You, Ji-Myoung;Lee, Hyun-Ho;Rhee, Shin-Hyung;Rhee, Key-Pyo
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.1
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    • pp.52-59
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    • 2012
  • Among many factors to be considered for higher safety level requirements, the hull stability in intact and damaged conditions in seaways is of utmost importance. Since the assessment of a damaged ship is complicated due to the highly non-linear behavior, it is widely acknowledged that computational fluid dynamics (CFD) methods are one of the most feasible approaches. Although many research activities are being reported on the damaged ship stability recently, most of them are not designed for validation of CFD studies. In this study, well-designed model tests were performed to build a CFD validation database, which is essential in developing better CFD methods for the damage stability assessment. The geometry of the damaged compartment and test conditions were determined based on preliminary CFD simulations. Free roll decay tests in calm water with both intact and damaged ships were performed and the roll motion characteristics were compared. The damaged ship showed a larger roll damping coefficient and more rapid decrease of roll amplitude than the intact ship. The primary reason of these efforts can be explained by the movement of the flooded water.

Experimental Study of the Free Roll Decay Test for the Evaluation of Roll Damping Coefficients (감쇠계수 산출을 위한 자유 횡동요 감쇠실험 연구)

  • Kim, Namwoo;Kim, Yong Jig;Ha, Youngrok
    • Journal of the Society of Naval Architects of Korea
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    • v.52 no.6
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    • pp.460-470
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    • 2015
  • In general ships and FPSOs, roll damping is very small and consequently roll motion is very large at the roll resonance frequency. Proper evaluation of the roll damping coefficient at the resonance frequency is an important task in the study of roll motion and usually it is done by the analysis of free roll decay tests. The relative decrement method based on energy relation has been used mainly for the evaluation of roll damping coefficient from the roll decay test so far. As another method, the logarithmic decrement method based on equivalent linear decay assumption can be used for the same purpose and it is relatively simple. In this paper, both of the relative decrement method and the logarithmic decrement method are used for the evaluation of roll damping coefficient including quadratic damping from the free roll decay tests, and their results are cross-checked for verifying the obtained damping coefficients. Through applications to a box-type floating body equiped with bilge keels, it is shown that the two methods give almost the same damping coefficients in a practical view point and the cross-check of their results is to be a good tool to prevent a possible error. And also the quantitative effects of the bilge keels on the roll damping of box-type floating body are shown and discussed.