• 대한조선학회논문집
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• 제55권3호
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• pp.187-195
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• 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
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• 제44권3호
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• pp.279-284
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• 2007

As a container vessel becomes larger, the bow flare becomes larger. The large bow flare structures are often subjected to dynamic pressure loads due to bow flare slamming occurring in rough seas. The aim of this paper is to investigate the characteristics of bow flare slamming pressure measured in a real voyage through the North Pacific Ocean. The characteristics of impact pressure load caused by slamming is addressed in terms of the pressure pulse-time history which involves rising time, peak pressure, decaying time and type of pressure decay. The values were presented using non-dimensional parameters.

• 대한조선학회논문집
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• 제47권3호
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• pp.410-420
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• 2010

When ships are sailing with large motions in rough waves, the slamming phenomenon occurs and the ships suffer from impulsive pressure loadings. Recently, ships are becoming lager and faster than before and it becomes more possible that the ships experience larger impacts on their bows and sterns. Many researchers have been performing the investigations on slamming experimentally and theoretically for a long time. Most of the research reported in the open literature focused on how to accurately estimate the amplitude of the peak pressure of slamming. According to the results of a recently published work, not only the amplitude of peak pressure but also the width of the peak may play an important role in predicting the extents of damage of impacted structures. The uncertainty of impulsive pressure loadings due to slamming has been indicated by many researchers. However, probabilistic treatments of the impulsive pressure loadings are few. In this study, drop tests were conducted on wedges having dead-rise angles of $0^{\circ}$ and $10^{\circ}$. Not only the amplitude of peak pressure but also the width of peak pressure were measured. Furthermore, the variations of those values are also provided for the probabilistic approach of the slamming problem.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권4호
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• pp.439-445
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• 2017

Plunging breaker slamming pressures on vertical or sloping sea dikes are one of the most severe and dangerous loads that sea dike structures can suffer. Many studies have investigated the impact forces caused by breaking waves for maritime structures including sea dikes and most predictions of the breaker forces are based on empirical or semi-empirical formulae calibrated from laboratory experiments. However, the wave breaking mechanism is complex and more research efforts are still needed to improve the accuracy in predicting breaker forces. This study proposes a semi-empirical formula, which is based on impulse-momentum relation, to calculate the slamming pressure due to plunging wave breaking on a sloping sea dike. Compared with some measured slamming pressure data in two literature, the calculation results by the new formula show reasonable agreements. Also, by analysing probability distribution function of wave heights, the proposed formula can be converted into a probabilistic expression form for convenience only.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.229-233
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• 2002

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. Therefore, the air pressure cylinder can be an alternative tool in slamming experiment.

• Journal of Advanced Research in Ocean Engineering
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• 제4권4호
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• pp.195-203
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• 2018

The wave impact on ships could cause local damage to the ship's hull, which has been a concerning issue during the ship design process. In recent years, local structural damages of ships caused by slamming loads have been reported by accident; therefore, it is necessary to study the local slamming pressure loads and structural response assessment. In the present study, slamming loads around the ship's bow region in the presence of regular wave have been simulated by RANS equations discretized with a cell-centered finite volume method (FVM) in conjunction with the $k-{\Box}$ turbulence model. The dynamic structural response has been calculated using an explicit FE method. By adding the slamming pressure load of each time step to the finite element model, establishing the reasonable boundary conditions, and considering the material strain-rate effects, the dynamic response prediction of the bow flare structure has been achieved. The results and insights of this study will be helpful to design a container ship that is resistant enough to withstand bow flare slamming loads.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1064-1081
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• 2014

This paper presents a numerical analysis of slamming and whipping using a fully coupled hydroelastic model. The coupled model uses a 3-D Rankine panel method, a 1-D or 3-D finite element method, and a 2-D Generalized Wagner Model (GWM), which are strongly coupled in time domain. First, the GWM is validated against results of a free drop test of wedges. Second, the fully coupled method is validated against model test results for a 10,000 twenty-foot equivalent unit (TEU) containership. Slamming pressures and whipping responses to regular waves are compared. A spatial distribution of local slamming forces is measured using 14 force sensors in the model test, and it is compared with the integration of the pressure distribution by the computation. Furthermore, the pressure is decomposed into the added mass, impact, and hydrostatic components, in the computational results. The validity and characteristics of the numerical model are discussed.

• 한국해양공학회지
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• 제21권1호
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• pp.40-44
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• 2007

This paper presents the experimental results on slamming phenomenon. The air pressure cylinder was used to ensure repeatability of the impact. The results showed that the adopted experimental technique was excellent in terms of repeatability, compared to that of the free drop tests. The pressure time histories, magnitude of peak pressure and the behavior of jetspray were obtained. The flat specimen was tested for various incident angles. To estimate the incident speed of the specimen, a high-speed camera was used. The high-speed camera was also a useful tool in understanding the behavior.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.518-530
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• 2020

The present study concerns the stern slamming load of container carriers, with stern bulb arrangement variation. First, a series of wedge drop tests were conducted using simple wedge models with fixed deadrise angles, and tests with the cross-section models of practical container carrier sterns were followed. The deadrise angle of the simple wedge ranged from 0° to 10°. The pressure measurement results of the simple wedge drop tests were distributed between empirical formula and analytic solution, so the experimental setup was validated. In the cases of practical hull cross-sections, the water entry of the bulb prior to that of the transom resulted in characteristic water film generation and delayed pressure peak appearance. The trapped air between the bulbs damped the pressure in the twin skeg hull case, reducing the pressure peak and causing the pressure oscillation during water entry.

• 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.