• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.575-589
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• 2008

In the present work, we investigate the hydrodynamic behavior of a turbulent bore, such as tsunami bore and tidal bore, generated by the removal of a gate with water impounded on one side. The bore generation system is similar to that used in a general dam-break problem. In order to the numerical simulation of the formation and propagation of a bore, we consider the incompressible flows of two immiscible fluids, liquid and gas, governed by the Navier-Stokes equations. The interface tracking between two fluids is achieved by the volume-of-fluid (VOF) technique and the M-type cubic interpolated propagation (MCIP) scheme is used to solve the Navier-Stokes equations. The MCIP method is a low diffusive and stable scheme and is generally extended the original one-dimensional CIP to higher dimensions, using a fractional step technique. Further, large eddy simulation (LES) closure scheme, a cost-effective approach to turbulence simulation, is used to predict the evolution of quantities associated with turbulence. In order to verify the applicability of the developed numerical model to the bore simulation, laboratory experiments are performed in a wave tank. Comparisons are made between the numerical results by the present model and the experimental data and good agreement is achieved.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.204-212
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• 2003

As the first step to investigate the nonlinear interactions between turbulence and marine structures inside a viscous NWT, a LES technique was applied to the turbulent channel flow for $Re_{T}=150$, in this paper. The employed models were 4 types, such as the Smagorinsky model, the Dynamic SGS model, the Structure Function model and the Generalized Normal Stress model. The simulated data in time-series for the LESs were averaged in both time and space and performed statistical analysis. And results of the LESs were compared with those of a DNS developed in the present study and two spectral methods by Yoon et al.(2003) & Kim et al.(1987). It seems to be quite difficult to evaluate their performances to the present problem, but is seen that the accuracy of LESs are still related to the number of grids(or fine grid size).

• Journal of the Society of Naval Architects of Korea
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• v.52 no.6
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• pp.471-477
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• 2015

When a ship sails in a seaway, the resistance on a ship increases due to incident waves and winds. The magnitude of added resistance amounts to about 15–30% of a calm-water resistance. An accurate prediction of added resistance in waves, therefore, is essential to evaluate the performance of a ship in a real sea state and to design an optimum hull form from the viewpoint of the International Maritime Organization (IMO) regulations such as Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI). The present study considers added resistance problem of AFRAMAX-class tankers with the conventional bow and Ax-bow shapes. Added resistance due to waves is successfully calculated using 1) a three-dimensional time-domain seakeeping computations based on a Rankine panel method (three-dimensional panel) and 2) a commercial CFD program (STAR-CCM+). In the hydrodynamic computations of a three-dimensional panel method, geometric nonlinearity is accounted for in Froude-Krylov and restoring forces using simple wave corrections over exact wet hull surface of the tankers. Furthermore, a CFD program is applied by performing fully nonlinear computation without using an analytical formula for added resistance or empirical values for the viscous effect. Numerical computations are validated through four degree-of-freedom model-scale seakeeping experiments in regular head waves at the deep towing tank of Hyundai Heavy Industries.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.126-134
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• 2020

In the case of an earthquake, the fluid storage structure generates hydraulic pressure due to the fluctuation of the fluid. At this time, the hydraulic pressure of the fluid changes not only the peaked acceleration of the earthquake but also the sloshing height of the fluid free water surface. Factors influencing this change in load include the shape of the seismic wave, the maximum seismic strength, the size of the fluid storage structure, the width of the structure, and the height of the fluid. In this study, the effect of the ratio between the height of the fluid and the width of the structure was investigated on the fluctuation characteristics of the fluid. 200mm and 140mm of fluid were placed in a water storage tank with a width of 500mm, and a real seismic wave was applied to measure the shape of the fluctuation of the fluid free water surface. The similarity between the experiment and the analysis was verified through the S.P.H(Smoothed Particle Hydrodynamic) technique, one of the numerical analysis techniques. It was confirmed that the free water surface of the fluid showed a similar shape, through comparison of experiment and analysis. And based on this results, SPH technique was applied to analyze the fluctuation shape of the fluid free water surface while varying the ratio between the fluid height and the structure width. An equation to predict the maximum and minimum heights of the fluid free water surface during an earthquake was proposed, and it was confirmed that the error between the maximum and minimum heights of the fluid free water surface predicted by the proposed equation was within a maximum of 3%.