• 제목/요약/키워드: slamming

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A Comparative Study on the Prediction of Bow Flare Slamming load using CFD and Prescript Formula for the Container Ship

  • Seo, Dae-Won;Jeon, Gi-Young;Song, Kang-Hyun
    • Journal of Advanced Research in Ocean Engineering
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    • 제4권4호
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    • pp.204-216
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    • 2018
  • A ship repeatedly face free surface under rough sea conditions owing to relative motion with wave encounter. The impact pressure is transferred to the hull structure and causes structural damage. In this study, the bow flare slamming load of a container ship is estimated using computations fluid dynamics (CFD) and prescript formula according to various classifications. It is found that the bow flare slamming load calculated by the formulas of the common structural rule and ABS tends to be similar to the CFD results.

선수파 및 사파조건에서 컨테이너선의 선수 플레어 슬래밍 하중 추정에 관한 수치적 연구 (Numerical Study on Prediction of Flare Slamming Load on Container Ship under Head Sea and Oblique Sea Conditions)

  • 서대원;오정근
    • 해양환경안전학회지
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    • 제25권4호
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    • pp.489-497
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    • 2019
  • 거친 해상 조건에서 운항하는 선박은 파도와의 상대운동으로 인해 슬래밍 하중에 노출된다. 특히 선수가 자유수면으로 입수하는 과정에서 선체부는 일시적으로 큰 슬래밍 충격하중을 받게된다. 일반적으로 대형 컨테이너선박의 경우, 큰 플레어를 가지는 특징이 있으며, 이로 인해 플레어 슬래밍 충격하중으로 인한 구조적 손상이 발생할 수 있다. 본 연구에서는 슬래밍 수치시뮬레이션을 위해 먼저 신뢰할 만한 실험결과와의 비교검증을 수행하였으며, 선수 및 사파에서 선수플레어 슬래밍 하중을 추정하였다. 그 결과 슬래밍 하중이 발생되는 위치는 0.975st이며, 최대 충격 하중은 선수파 조건에서 약 475kPa임을 확인하였다.

슬래밍 충격하중을 고려한 선체 휘핑 해석 (Whipping analysis of hull girders considering slamming impact loads)

  • 박성환;이근배;임채환
    • 대한조선학회논문집
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    • 제37권3호
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    • pp.99-109
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    • 2000
  • 본 연구에서는 대파고 파랑 중을 항해하는 선박의 슬래밍 충격에 대한 선체 전체의 동적 탄성응답 해석법을 개발하였다. 선체구조는 전단효과를 고려하는 박판보 유한요소이론을 활용하였으며, 선체 각 단면에 작용하는 유체력은 통상의 선형 운동체 이론에 덧붙여 물체 경계의 비선형성을 고려하여 추정하였다. 즉 매 순간 선체와 파 입자간의 접수 형상을 고려하는 비선형 유체력 추정법을 모멘텀 슬래밍 이론에 근거하여 정식화하였다. 개발된 해석법의 검증을 위해 V형 단면 선형과 S-175 선형 모델을 대상으로 수치해석을 수행하였다. 시간 영역에 있어 각 단면에서의 파면에 대한 상대 변위 성분과 속도 성분들을 계산하였으며, 선체 중앙 단면에서의 굽힘 모멘트 값의 시간이력을 검토하였다.

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슬래밍 충격 압력에 대한 연구 (A Study on Slamming Impact Pressure)

  • 박준수;오승훈;권순홍;정장영
    • 한국해양공학회지
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    • 제23권1호
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    • pp.67-73
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    • 2009
  • This study presents the results of a slamming experiment using a pneumatic cylinder. The employment of the pneumatic cylinder showed a relatively good repeatability when the results were compared with those of other slamming devices. The experiment was done for various incident angles. An air pocket was believed to cause a reduction in the magnitude of the impact pressure with an incident angle of $0^{\circ}$ for the water entry. A high speed camera was used in an attempt to locate the time of the contact between the bottom of the specimen and the free surface. It seemed that the maximum pressure occurred before the water contacted the bottom of the specimen.

Slamming충격으로 인한 선체의 구조적 응답해석 (Analysis on the Structual Response of Ship Structures Subjected to Slamming Impact)

  • 구자삼;홍봉기
    • 수산해양기술연구
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    • 제21권1호
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    • pp.67-74
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    • 1985
  • 본 논문에서 얻은 결과를 요약하면 다음과 같다. 1) slamming 충격력에 의한 선각의 굽힘 모우멘트와 전단력의 계산은 본 논문의 이론 전개방법에 의해 구하는 것이 Antonides의 적용 방법보다 더 타당하다고 생각된다. 2) 수치계산 예에서 보면 선체 중앙단면에서 가장 큰 sagging moment가 발생하며 Antonides의 결과치 보다 3~5%정도 더 크게 나타났다. 3) 기준진동형의 중첩항 수는 주어진 문제의 특성 및 요구되는 정도에 따라 결정되어야 하므로 고차 진동형에 대한 실측치와 이론치의 비교 분석이 선행되어야 한다고 생각된다.

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Experimental and Numerical Study on Slamming Impact

  • Kwon, Sun Hong;Yang, Young Jun;Lee, Hee Sung
    • 한국해양공학회지
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    • 제27권1호
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    • pp.1-8
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    • 2013
  • This paper presents the results of experimental and numerical research on the slamming phenomenon. Two experimental techniques were proposed in this study. The traditional free drop tests were carried out. However, the free drop tests done in this study using an LM guide showed excellent repeatability, unlike those of other researchers. The coefficients of variation for the drop test done in this experiment were less than 0.1. The other experimental technique proposed in this study was a novel concept that used a pneumatic cylinder. The pneumatic cylinder could accelerate the specimen over a very short distance from the free surface. As a result, high rates of repeatability were achieved. In the numerical study, the development of in-house code and utilization of commercial code were carried out. The in-house code developed was based on the boundary element method. It is a potential code. This was mostly applied to the computation of the wedge entry problem. The commercial code utilized was FLUENT. Most of the previous slamming research was done under the assumption of a constant body velocity all through the impact process, which is not realistic at all. However, the interaction of a fluid and body were taken into account by employing a user-defined function in this study. The experimental and numerical results were compared. The in-house code based on BEM showed better agreement than that of the FLUENT computation when it cames to the wedge computation. However, the FLUENT proved that it could deal with a very complex geometry while BEM could not. The proposed experimental and numerical procedures were shown to be very promising tools for dealing with slamming problems.

직교격자계 기반의 수치계산법을 이용한 슬래밍 충격압력의 연구 (A Study on Slamming Impact Pressure by a Numerical Method based on the Cartesian-grid System)

  • 김기용;이영길;하윤진;강의하;박정호;이선규;이창진
    • 대한조선학회논문집
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    • 제56권4호
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    • pp.308-315
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    • 2019
  • In this study, numerical simulations of slamming impact pressure acting on the flat plate and wedge type models using the cartesian-grid system and Modified Marker-Density Method (MMD method) were performed and the results were examined. The flat plate and wedge type models were selected as target objects, the turbulence characteristics were considered by applying the Sub-Grid Scale (SGS) turbulence model. Through this study, how the pressure acting on the target objects according to the incident angle influences the slamming impact pressure was examined and the results were compared with the flow characteristics of other experimental results. Also, the degree of slamming impact pressure is evaluated with respect to the cartesian-grid system and MMD method, which is easy to use and has a high degree of calculation for free surface.

입수 충격 하중에 관한 실험적 연구 (The Water Entry Fluid Load Experimental Analysis)

  • 정두진;이희성;권순홍;송기종;정병훈
    • 한국해양공학회:학술대회논문집
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    • 한국해양공학회 2003년도 추계학술대회 논문집
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    • pp.183-186
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    • 2003
  • This paper presents the results of slamming experiment using air pressure cylinder to increase the repeatability of the experiment. When it comes to the slamming experiment, the traditional way of doing it has been the free fall experiment. By adopting air pressure cylinder almost equal peak pressures were obtained with that of free fall experiment. Jet takes place when the wedge enters water. Slamming doesn't take place when Dead rise angle is more then 20 degrees.

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Effect of Structural Elasticity on Slamming Against Wetdecks of Multihull Vessels

  • Kvalsvold, Jan;Faltinsen, Odd M.;Aarsnes, Jan V.
    • Journal of Ship and Ocean Technology
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    • 제1권1호
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    • pp.1-14
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    • 1997
  • Hydroelastic slamming against the wetdeck of a multihull vessel is studied numerically and experimentally. The beam equations and a two-dimensional flow model are used to find the dynamic stresses in longitudinal stiffeners between two transverse stiffeners. The largest stresses in the structure occur in the time scale of the lowest wet natural period of the beam. A simple relation between the maximum stress, the local geometry and the impact velocity of the wetdeck is established. The stresses in the wetdeck are neither sensitive to the radius of curvature of the waves nor where the waves initially hit the wetdeck. It is concluded that the maximum impact pressure should not be used to find maximum bending stresses during wetdeck slamming.

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유체-구조 상호 간섭을 고려한 쐐기 슬래밍에 대한 실험적 연구 (Experimental Study on Wedge Slamming Considering Fluid-Structure Interaction)

  • 안강수;권순홍
    • 한국해양공학회지
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    • 제31권1호
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    • pp.22-27
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    • 2017
  • This paper presents the results of an experimental study on the wedge slamming impact problem, including the fluid-structure interaction. A free drop test was performed to estimate the hydroelasticity. Three wedges were fabricated of 5 mm thick steel plate. The deadrise angles were $15^{\circ}$, $20^{\circ}$, and $25^{\circ}$. Plate thicknesses of 2 mm and 3 mm were used to determine the effect of the structural rigidity. The drop heights were 25 cm, 50 cm, 75 cm, and 100 cm. The pressure on a rigid part of the wedge and strain of the elastic plate were measured at four different locations. The pressure was compared using the Wagner theory and generalized Wagner theory.