• 대한조선학회논문집
• /
• 제55권3호
• /
• pp.187-195
• /
• 2018

Ship's bottom slamming has been studied by many researchers for a very long time. But still some ships suffer structure damages caused by the bottom slamming impacts. This paper presents a practical computation method of the design impact pressure due to ship's bow bottom slamming. Large heave and pitch motions of a rigid hull ship are simulated by the nonlinear strip method in time domain and the relative colliding velocity between the bow bottom and the water surface is calculated using the simulated ship motions. The bottom slamming impact pressure is calculated as a product of the relative colliding velocity squared and the bottom slamming pressure coefficient that is obtained by modification of the SNAME pressure coefficients based on Ochi's slamming experiments. Not only the bottom slamming pressures but also the required bottom plate thicknesses are calculated and compared with those of the classification society rules. The comparisons show good agreements and it is confirmed that the present method is practically very useful for the bottom structure design against ship's bow bottom slamming impacts.

• 대한조선학회논문집
• /
• 제51권6호
• /
• pp.503-509
• /
• 2014

This paper describes the time-domain numerical method for prediction of slamming loads on a ship in waves using the strip theory. The slamming loads was calculated considering the relative vertical velocity between the instantaneous ship motion and wave elevation. For applying the slamming force on a ship section, the momentum slamming theory and the empirical formula-based bottom slamming force were used corresponding to the vertical location of wetted body surface. Using the developed method, the vertical bending moments, relative vertical velocities, and impact forces of S175 containership were compared in the time series for various section locations and wave conditions.

• Ocean Systems Engineering
• /
• 제5권4호
• /
• pp.245-259
• /
• 2015

The numerical simulation of wave slamming on a 3D platform deck was investigated using a coupled Level-Set and Volume-of-Fluid (CLSVOF) method for overset grid system incorporated into the Finite-Analytic Navier-Stokes (FANS) method. The predicted slamming impact forces were compared with the corresponding experimental data. The comparisons showed that the CLSVOF method is capable of accurately predicting the slamming impact and capturing the violent free surface flow including wave slamming, wave inundation and wave recession. Moreover, the capability of the present CLSVOF method for overset grid system is a prominent feature to handle the prediction of wave slamming on offshore structure.

• 수산해양기술연구
• /
• 제19권2호
• /
• pp.117-124
• /
• 1983

정면규칙파중에서 Bow-flare부 충격은 선저충격에 비해서 작용 시간이 길고, 선체 수직운동진폭이 큰 상태이거나, 파고가 큰 입사파가 적용되는 경우에 선체에 작용하는 충격력은 상당히 크며, 파고가 높아지면, 발생하는 모우멘트도 증가한다. 2. Bow-flare부가 큰 선형의 경우에는 선저노출이 일어나지 않더라도 부가질량의 급격한 증가에 따라 상당히 큰 충격력이 작용한다. 3. Deckwetness, 불규칙파중에서의 응답해석, 상대변위를 구할 때 Dynamic Swell-up의 양을 고려한 계산 등의 검토가 요망된다.

• Journal of Ship and Ocean Technology
• /
• 제4권1호
• /
• pp.21-27
• /
• 2000

The slamming force occurring in the free fall impact of cylindrical bodies on the water surface is analyzed in both compressible and incompressible stages. In the compressible phase the hydrodynamic analysis is carried on by the acoustic approximation, obtaining a closed form expression for the maximum impact force. The incompressible analysis is approached through and unsteady boundary element method to compute the free surface evolution and the slamming force on the body. A similar behavior seems to characterize the maximum slamming force versus a dimensionless mass parameter.

• Ocean Systems Engineering
• /
• 제10권2호
• /
• pp.163-179
• /
• 2020

Considering the huge demand of several types of subsea equipment, as Christmas Trees, PLEMs (Pipeline End Manifolds), PLETs (Pipeline End Terminations) and manifolds for instance, a critical phase is its installation, especially when the equipment goes down through the water, crossing the splash zone. In this phase, the equipment is subject to slamming loads, which can induce impulsive loads in the installation wires and lead to their rupture. Slamming loads assessment formulation can be found in many references, like the Recommended Practice RP-N103 from DNV-GL (2011), a useful guide to evaluate installation loads. Regarding to the slamming loads, RP-N103 adopt some simplifying assumptions, as considering small dimensions for the equipment in relation to wave length, in order to estimate the slamming coefficient C_S used in load estimation. In this article, an experimental investigation based on typical subsea structure dimensions was performed to assess the slamming coefficient evaluation, considering a more specific scenario in terms of application, and some reduction of the slamming coefficient is achieved for higher velocities, with positive impact on operability.

• 한국해양공학회지
• /
• 제29권2호
• /
• pp.163-168
• /
• 2015

This paper presents the results of experimental work on the wedge slamming impact problem. An experiment was done with a wedge model. The deadrise angle of the wedge was $4^{\circ}$. The model was made in two parts: the outside part was made of a 5-mm-thick steel plate that could be assumed to be a rigid body, and the inside part was made of a thin SUS plate that could be assumed to be an elastic body. Thin SUS plate thicknesses of 2 mm and 3 mm were used to determine the effect of plate rigidity. The drop height was varied from 0.25 m to 1 m to determine the effect of a large deformation.

• 선박안전
• /
• 통권31호
• /
• pp.60-70
• /
• 2011

The slamming impact pressures at the bottom area of the Open60' are evaluated by the rules and regulations of various organizations - ISO and classification societies. The enhanced performance of the modern racing yacht in terms of speed which achieves well over 20 knots needs special consideration. The calculated design impact pressures are compared a experimental results. Severe difference can be found in these calculation results but the final conclusion shall be obtained after the scantling calculation under the evaluated design impact pressure so far.

• 대한조선학회논문집
• /
• 제56권4호
• /
• pp.308-315
• /
• 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.

• 해양환경안전학회지
• /
• 제25권4호
• /
• pp.489-497
• /
• 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.