Se-min Jeong

CFD Simulation of Methane Combustion for Estimation of Fire and Explosion in Offshore Plant

Because of the recent increase in maritime cargo capacity, the production and price of crude oil have been rising. As oil prices have risen, many problems have occurred in the industry. To solve these problems, marine resources are being actively developed, and there has been an increase in the orders for special vessels and marine structures for the development of marine resources. However, consequently, various kinds of accidents have also occurred in these special vessels and structures. One of the major types of accidents involves fire and explosion, which cause many casualties and property damage. Therefore, various studies to estimate and prevent such accidents have been carried out. In this study, as basic research for the prevention of fire and explosion, numerical simulations on combustion were carried out by using a commercial grid generation program, Gridgen, and a CFD program, ANSYS -CFX. The influences of some parameters, such as the grid system, turbulence model, turbulent dissipation rate, and so on, on the simulation results were investigated, and optimum ones were chosen. It was found that the present results adopting these parameters agreed moderately well with other experimental and numerical ones.

Applications of Three-Dimensional Multiphase Flow Simulations for Prediction of Wave Impact Pressure

In this study, the impact loads on tank walls by sloshing phenomena and on a tall structure in a three-dimensional rectangular tank were predicted using multiphase flow simulations. The solver was based on the CIP/CCUP (Constraint interpolation CIP/CIP combined unified procedure) method, and the THINC-WLIC (Tangent hyperbola for interface capturing-weighted line interface calculation) scheme was used to capture the air- water interface. For the convection terms of the Navier-Stokes equations, the USCIP (Unsplit semi-lagrangian CIP) method was adopted. The results of simulations were compared with those of experiments. Overall, the comparisons were reasonably good.

Development of WMLS-based Particle Simulation Method for Solving Free-Surface Flow

In general, particle simulation methods such as the MPS(Moving Particle Simulation) or SPH(Smoothed Particle Hydrodynamics) methods have some serious drawbacks for pressure solutions. The pressure field shows spurious high fluctuations both temporally and spatially. It is well known that pressure fluctuation primarily occurs because of the numerical approximation of the partial differential operators. The MPS and SPH methods employ a pre-defined kernel function in the approximation of the gradient and Laplacian operators. Because this kernel function is constructed artificially, an accurate solution cannot be guaranteed, especially when the distribution of particles is irregula r. In this paper, we propose a particle simulation method based on the moving least-square technique for solving the partial differential operators using a Taylor-series expansion. The developed method was applied to the hydro-static pressure and dam-broken problems to validate it.

2-Dimensional Moving Particle Simulation for Prediction of Oil Boom Performance in Waves

Oil booms are one of the most widely used types of equipment for the protection of coastal areas against oil spills. In some situations, however, there are several types of oil leaks from the oil boom. Important factors regarding these phenomena include the surrounding ocean environment, such as waves, the density and viscosity of oil, the length of the oil boom skirt, etc. To estimate the performance of the oil boom, it is necessary to predict the behavior of the spilled oi l and oil boom. In the present study, the prediction of oil boom performance in waves was carried out using the Pusan-National-University-modified Moving Particle Semi-implicit (PNU-MPS) method, which is an improved version of the original MPS proposed by Koshizuka and Oka (1996). The governing equations, which consist of continuity and Navier-Stokes equations, are solved by Lagrangian moving particles, and all terms expressed by differential operators in the governing equations are replaced by the particle interaction models based on a kernel function. The simulation results were validated through a comparison with the results of Violeau et al. (2007)..

Estimation of Wave Loads Acting on Stationary Floating Body Using Viscous Numerical Wave Tank Technique

In the present study, a flow analysis for estimating the wave loads acting on a stationary floating body inside a viscous numerical wave tank was performed using the commercial software FLUENT. T he governing equations for the viscous and incompressible fluid motion were the continuity and Navier- Stokes equations, and a piston-type wavemaker was employed to reproduce wave environments. First, the optimal simulation conditions were derived through numerical tests for the wavemaker and wave absorber, and then the wave loads and wave run-up on a vertical truncated cylinder were estimated and compared with the experimental and other numerical results.

Stability Evaluation of Floating Dock during Construction and Launching of Caisson for Breakwater

In general, huge caissons for breakwaters have been constructed on land or a floating dock. In the case of the construction on a floating dock, a 4 step installation procedure is involved: i) construction on a floating dock, ii) transportation by the floating dock to an area near the target sea, iii) launching from the floating dock, and iv) transference by tug-boats to the installation site. It is especially important to pay attention to the dynamic stability of the floating dock against the conditions in the sea during steps i) and iii). In this paper, the static and dynamic stabilities of a caisson on a floating dock are evaluated based on IMO rules during the construction and launching of the caisson on a floating dock by using independent commercial S/Ws such as NAPA, WAMIT, and CHARM3D.

Preliminary study for development of marine hydropower system using Tidal Jet Generator

To prevent the harmful effect of global warming, development of renewable energy source comes into the spotlight. In these days, the nations, which are located in near shore like South Korea and some European nations, have been developing renewable energy systems from ocean energy. However, to develop the Ocean energy, it spends too much expenses. For example, over the 4 billion dollar was spent for the construction of the Sihwa tidal power station. And it causes some environmental problems. In this study, preliminary study for the development of marine hydropower was conducted. The marine hydropower system proposed in this study is utilizing the Tidal Jet Generator (TJG) for generating electricity. During both phases of tide, strong and uni-directional jets can be obtained locally from the inlet of the TJG, due to the water level difference between the inner and outer sides of TJG. Therefore we supposed that tidal jet can be harnessed as the renewable energy source. To conduct this study, theoretical equation based on Torricelli equilibrium was used for calculating the maximum velocity from TJG. From the result, the duration time for generating TJG was too short to apply for renewable energy source. We supposed that Torricelli equilibrium ignores the viscous force. Thus computational fluid dynamics (CFD) was applied to calculating the velocity and duration time. CFD results which considered the viscous force and shape of outlet represents that CFD result is different from theoretical result. And CFD results will be compared with the experimental result. The hydraulic experiment will be performed based on model size.