• Special Issue of the Society of Naval Architects of Korea
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• 2015.09a
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• pp.50-55
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• 2015

Application of newly conceptualized Anti-Splash Devices designed for COT vent pipes were studied on a P/V valve located on the upper deck of an oil carrier vessel. Anti-Splash devices are used in the shipbuilding industry in order to avoid oil overflow and spray accidents caused by excess pressure and vacuum condition in the cargo oil tanks. These conditions are caused by the transverse and longitudinal sloshing forces that arise from ship motion during sea voyages. The main issue with existing Anti-Splash device model is flux at the outlet of the Anti-Splash Device, and so, new conceptual models for the Anti-Splash device were developed and compared to existing Anti-Splash device model using CFD analysis. Transient analysis was used to capture the flow and velocity of each model and a comparative analysis was performed between old and new-concept models. This data was used to determine the optimal design parameters in order to develop an optimized Anti-Splash Device. A Factory acceptance test was performed on the new-concept models in order to verify the performance and efficiency against their design requirements and other criterion. The final step performed was to apply the optimized Anti-Splash Device models for COT vent pipes to an actual vessel and verify performance through a seawater cargo operation during a sea voyage as per the ship owner's request. The patent for the aforementioned device was obtained by the Korean Intellectual property Office dated Dec. 18th,2014.

• Journal of Korea Water Resources Association
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• v.34 no.2
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• pp.187-195
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• 2001

In this study, a numerical model describing the shallow-water equations is newly developed by using a TVD scheme. The model has a second-order accuracy in time and space and is free from nonphysical oscillations, even in the vicinity of large gradients. Because a upwind based TVD scheme requires a Riemann solver, the HLLC scheme is employed in this model. To calibrate the applicability and accuracy, the developed model is used to simulate dam-break waves in an ideal channel and a sloshing flow n a paraboloidal basin. Agreements between numerical predictions and analytical solutions are very resonable.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.53-58
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• 2013

Recently, some fluid-structure interaction (FSI) problems involving the fluid impact loads interacting with structures, such as sloshing, slamming, green-water, etc., have been considered, especially in the ocean engineering field. The governing equations for both an elastic solid model and flow model were originally derived from similar continuum mechanics principles. In this study, an elastic model based on a particle method, the MPS method, was developed for simulating the FSI problems. The developed model was first applied to a simple cantilever deflection problem for verification. Then, the model was coupled with the fluid flow model, the PNU (Pusan National University modified)-MPS method, and applied to the numerical investigation of the coupling effects between a cantilever and a mass of water, which has variable density, free-falling to the end of the cantilever.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.265-269
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• 2006

Anti-Roll Tanks, also called Sloshing Tanks, is a rather common and sometimes an efficient method of limiting the roll angles. The important parameters, when considering using anti-roll tanks, are positioning, size, duct area, flow control device etc. Measurement by the PIV(Particle Image Velocimetry) was conducted to investigate the flow characteristics around control damper and inlet area of duct for three kind of inclined angle $(\alpha=0^*,\;10^*\;and\;20^*)$. Flow behaviors such as instantaneous and time-mean velocity vectors are investigated. Furthermore, to reveal boundaries between flowing and stagnant zones and to extract velocity profiles at any selected sections of the lower duct for passive anti-rolling tanks system.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.104-117
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• 1991

When a body starts to move, the flow near the intersection point between a body and a free surface changes violently and rapidly in a very short initial time interval. This flow phenomena must be investigated whenever one treats the interaction between a body and a fluid, such as the motion of a floating body, sloshing in a tank, wave maker problem, entry of a body into a fluid etc.. Until Roberts(1987), it was widely accepted that a singularity exists at the intersection point. However, he showed that the singularity does not exist if a body moves non-impulsively. In this paper, an analytical solution cosistent for the case of impulsive motion of a body is obtained by including the effect of surface tension. From the characteristics of the newly obtained solution, a critical value associated with an oscillating phenomenon is found, and further more, it is shown that the oscillating phenomenon does not appear in the region where the distance form the intersection point is less than this critical value.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.4
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• pp.342-349
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• 2023

In this study, a numerical simulations were conducted to analyze the phase change behavior of a liquid hydrogen storage container. The effects of gravity direction and hydrogen filling rate on boil-off gas (BOG) in the storage container were investigated. The study employed the volume of fluid, which is the phase change analysis model provided by ANSYS Fluent (ANSYS, Canonsburg, PA, USA), to investigate the sloshing phenomenon inside the liquefied hydrogen fuel tank. Considering the transient analysis time, two-dimensional simulation were carried out to examine the characteristics of the flow and thermal fields. The results indicated that the thermal flow characteristics and BOG phenomena inside the two-dimensional liquefied hydrogen storage container were significantly influenced by changes in gravity direction and hydrogen filling rate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1538-1551
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• 1997

Kinetic energy conservation for fixed and moving grids is examined in time-accurate finite element computation of fully unsteady inviscid flows. As numerical algorithms, fractional step method (FSM) and modified SIMPLE are used. To simulate the flow in moving grid system, arbitrary Lagrangian-Eulerian (ALE) method is adopted. In the present study, the energy conserving time integration rule for finite element algorithm is proposed and discussed schematically. It is shown that the discretization by Crank-Nicolson in time and Galerkin (central difference) in space must be used to ensure energy conservation. The developed code has been tested for a standing vortex in fixed or moving grid system, sloshing in a tank and propagation of a solitary wave, and has been shown to be a completely energy conserving algorithm.

• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.46-51
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• 2006

Moonpool characteristics of a cleaning skip related with the performance of a skip are experimentally investigated. Resistance performances of the ship and flow patterns in the moonpool are observed, in order to determine the effect of different shaped moonpool. The ways to reduce ship pithing motion caused by force in the moonpool are examined. Experimental results, using a scale model of cleaning ship with moonpool, show that the step arranged in tier under water leads to significant improvements in performance, such us resistance and ship pithing motion. Depending upon the shape of step in the moonpool, the results indicate that the increment of resistance performance may be up to 35%, especially in the case of no step or high step.

• Journal of Ocean Engineering and Technology
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• v.36 no.1
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• pp.21-31
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• 2022

In recent years, various studies have been conducted on oscillating-water-column-type wave energy converters (OWC-WECs) with multiple chambers with the objective of efficiently utilizing the limited space of offshore/onshore structures. In this study, a numerical investigation based on a numerical wave tank was conducted on single, dual, and triple OWC chambers to examine the hydrodynamic performances and the energy conversion characteristics of the multiple water columns. The boundary value problem with the Laplace equation was solved by using a numerical wave tank based on a finite element method. The validity of the current numerical method was confirmed by comparing it with the measured data in the previous experimental research. We undertook a series of numerical simulations and observed that the water column motion of sloshing mode in a single chamber can be changed into the piston motion of different phases in multiple OWC chambers. Therefore, the piston motion in the multiple chambers can generate considerable airflow at a specific resonant frequency. In addition, the division of the OWC chamber results in a reduction of the time-dependent variability of the final output power from the device. As a result, the application of the multiple chambers leads to an increase of the energy conversion performance as well as a decrease of the variability of the wave energy converter.

• Journal of Korea Water Resources Association
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• v.43 no.10
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• pp.911-920
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• 2010

The closed water bodies, such as reservoirs and lakes, could be contaminated by an inflow of pollutants in the upstream as well as a stratification caused by seasonal natural phenomena. The vertical circulation particularly plays an important role in reduction of environmental pollutants. The factors of the vertical circulation are the temperature, wind, thermal diffusivity and sunlight. The wind is probably the most significant factor among them. Thus, it is necessary to describe the validation and application of a three-dimensional numerical model of wind-induced circulation in a thermally stratified flow. In this paper, a three-dimensional numerical model for the thermally stratified flows is presented. The model is conducted in three steps to calculate the velocity components from the momentum equations in x- and y- axis directions, the elevations from the free surface equation and the temperature from the scalar transport equation. Numerical predictions are compared with available analytical solutions for the sloshing free surface movement in a rectangular basin. The numerical results generally show a reasonable agreement with analytical solutions. And the model is applied to the circulation for the wind induced flow in a thermally stratification. Consequently, the developed model is validated by two verifications and phenomena of the internal flow.