• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.161-165
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• 2013

In this paper, possibility of controlling motion of a floating structure using a tuned liquid damper (TLD) is numerically investigated. A TLD is a tank partially filled with liquid. Sloshing phenomena of liquid inside a tank can suppress movement of the tank subject to external excitations at specific frequency. The effects of sloshing phenomena inside a rectangular floating body on its sway motion are investigated by varying excitation frequency. First, a grid-refinement study is carried out to ensure validity of grid independent numerical solutions using present numerical techniques. Then, sway motion of the floating body subjected to wave with five different frequencies are simulated. The normalized amplitudes of sway motion of the target floating body are compared over the frequency, for cases with and without water inside the floating body. It is shown that the motion of the floating body can be minimized by matching the sloshing natural frequency to excitation frequency.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.662-668
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• 2013

In this paper, possibility of controlling motion of a floating structure using a tuned liquid damper (TLD) is numerically investigated. A TLD is a tank partially filled with liquid. Sloshing motion of liquid inside a tank is known to suppress movement of the tank subject to external excitations at specific frequency. The effects of sloshing phenomena inside a rectangular floating body on its surge motion are investigated by varying external excitation frequency. First, a grid-refinement study is carried out to ensure validity of grid independent numerical solutions using present numerical techniques. Then, surge motion of the floating body subjected to external wave is simulated for five different excitation frequencies of which the center frequency equals to the natural frequency of internal liquid sloshing. The normalized amplitudes of surge motion of the target floating body are compared according to the excitation frequency, for the cases with and without water inside the floating body. It is shown that the motion of the floating body can be minimized by matching the sloshing natural frequency to the excitation frequency.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.630-633
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• 2008

A particle method has been developed for analyzing the motion of 2-D floating body in waves. The particle method is based on the MPS(Moving Particle Semi-implicit) method suggested by Koshizuka et al. (1996), and the flow motion coupled with the motion of floating body can be simulated. The wavemaker and wave absorber are installed at the inflow and outflow boundaries in a computational domain, respectively. The motion characteristics of a floating body is investigated numerically under the various computational conditions.

• Journal of Ocean Engineering and Technology
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• v.33 no.1
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• pp.10-16
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• 2019

The aim of this study was to improve the vertical motion performance of floating marina structures and to optimize the shapes of the structures for the Korea coastal environment. The floating body is connected to a plate-shaped submerged body through a connecting line under the water that has a stiff spring that serves to reduce the heave response. This system, which has two degrees of freedom, was modelled to analyze the interaction between the floating body and the submerged body. The vertical motion of the two-body system was compared with the motion of a single body to verify that the system could perform as an optimized model.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.6
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• pp.485-491
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• 2017

An experimental study on the reduction of vertical motion of floating body using floating-submerged body interaction was performed in a two-dimensional wave channel. The system consisting of a floating and submerged body that only move vertically was modeled. This experiment was designed based on the results of theoretical analysis of two-body interaction. The results showed a tendency to significant reduction of heave RAO of floating body due to submerged body. Various connection line stiffness and dimension of the submerged body were applied to investigate the effect of two-body interaction on the vertical motion of the bodies, Heave RAOs of the floating-submerged body were compared with those of single body. From the comparison study, we obtained an optimum condition of connection line and dimension of submerged body for maximum heave reduction at the resonant period of single body.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.407-416
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• 2023

Demand for leisure facilities such as mooring facilities for berthing leisure vessels and floating pensions based on floating bodies is increasing owing to the rapid growth of the population and related industries for marine leisure activities. Owing to its relatively light weight as a fluid, inclination is easily generated by waves and surcharges flowing to the coast, resulting in frequent safety accidents because of the low stability. As a solution to this problem, a motion reduction device for floating bodies is proposed in this study. The device (motion reduction device based on the air pressure dif erence) was attached to a floating body and the effect was analyzed by comparing the results with those of a floating body without motion reduction. The effect analysis was further analyzed using a computer analysis test, and the method for increasing the stability of the floating body was studied, and its the effect was verified. Based on the analysis of the test results, the stability of the floating body increased with a motion damping device is higher than that of the floating body without a motion reducing device as the wave momentum reduces, owing to the air pressure difference. Therefore it was concluded that the use of such a device for reducing motion a floating body is useful not only for non-powered ships but also for powered and semi-submersible ships, and further research should be conducted by applying it to various fields.

• International Journal of Ocean System Engineering
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• v.4 no.1
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• pp.43-48
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• 2014

Varying bathymetry significantly affects on the wave propagation and motion response of floating body. Coupled-mode wave theory is adopted to describe the incident wave properly in varying region. The results of waves and motion response are compared to those from numerical wave tank, and the agreement is favorable. The sloped bottom is modeled and its effect on the floating body is discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.5
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• pp.410-418
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• 2009

Based on a linear potential theory, the boundary element method(BEM) is developed and applied to analyze the hydrodynamic forces and the motion responses of a floating body with a partially reflective sidewall. The hydrodynamic forces (added mass and damping coefficients) are dependent on not only the submergence of a floating body and the reflection of a sidewall, but also the gap between body and sidewall. In particular, the partial reflection of a sidewall plays an importance role in the motion responses of a floating body at resonant frequencies. It reduces the resonant peaks caused by resonance phenomenon due to the wave trapping in an enclosed fluid domain between body and sidewall. Developed predictive tools can be used to assess the motion performance of a floating body for various combinations of configuration of a floating body, wave heading, sidewall properties, and wave characteristics and applied to supply the basic informations for the harbour design considering the motion characteristics of a moored ship.

• Journal of Multimedia Information System
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• v.7 no.4
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• pp.269-276
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• 2020

The small craft including jet-board for leisure are commonly smaller than the general commercial vessels. For the floating vessel, the motion analysis is significantly important component to design the shape. It is, however, hardly predicting its behavior by using conventional boundary element method due to violating small amplitude assumption for potential theory. The computational fluid dynamics method can afford to simulate such small craft, but its grid system was not able to calculate motion, because movable body disturbs the grid system by confliction. The dynamics fluid body interaction model with over-set mesh system can be dealt with movable floating body under irregular ocean wave. In this study, several cases were considered to reveal that DFBI is essential method to predict floating body motion. The single phase simulate was conducted to establish the shape perfection, and then the validated vessel was simulated with ocean waves weather DFBI option on or off. Through the comparison, the results between the cases of DFBI on and off shows significantly difference. It was claimed that the DFBI was necessary not only to calculation body motion, but also to predict accurate drag and lift force on the floating body for small size craft.

• Journal of Ocean Engineering and Technology
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• v.11 no.1
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• pp.65-73
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• 1997

The floating body discussed in this study is a 2-D rectangular floating unit supported by four vertical piles at its corners. Structures of this type are frequently seen as floating piers for the crafts in a small harbour. The movement in some modes of motion of such a flating body is fully or partially restrincted by the piles. The authors(Kim et al. 1994) carried out a series of model tests on its wave control function, its motion and the loads on piles. The experimental results showed that a certain degree of intial constriction force which clamps the floating unit in the horizontal direction can effectively reduce the body motion and wave energy without increasing mooring forces. This may be due to the friction forces occuring between the piles and the rollers installed in the mooring equipments on the floating unit. In this paper, we develop a numerical model for the prediction of wave transformation and floating body motions, where the friction force is idealized as the Coulomb friction and linearized into a damping force using the equivalent damping cofficient. This linearization is verified by comparing the results of motions between the linear and nonlinear analysis of the ezuations of motion. We further compare the caculation results by the linear model with the experimental results and discuss the effect of the friction force or the constriction force on body motions and wave energy dissipation.