• Korea-Australia Rheology Journal
• /
• v.13 no.3
• /
• pp.131-139
• /
• 2001

A coupled approach is proposed for the prediction of sheet profile in sheet casting process, which combines one-dimensional analytical method on planar elongational flow region and three-dimensional numerical method on the other region. The strategy is constructed from the observations that the flow domain of sheet casting process can be separated into two parts based old the flow kinematics. The flow field in the central region of sheet, over which the planar elongational flow dominates, is possibly replaced by one-dimensional analytical solution. Then only a partial flow domain near the edge region of sheet, where the flow kinematics cannot be described by the planar elongational flow itself, requires three-dimensional numerical simulation. Good agreement is observed between the coupled approach developed in this study and the full three-dimensional numerical simulation previously developed and reported by the authors. This coupled approach may have provided flexibility with low costs to accommodate a wide range of die sizes in sheet casting process.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2003.05a
• /
• pp.51-59
• /
• 2003

Marine Casualty Forecasting System (MCFS) is to broadcast the prediction number and risk level of marine casualties as like daily weather forecasting. The MCFS consists of marine casualty numerical D/B, prediction model and, three-dimensional statistics visualization system. The implementation procedure for the numerical D/B is described in the paper. The data relating to a total of 724 ship casualties in the west-southern sea area (latitude 33$^{\circ}$N∼35$^{\circ}$ and longitude 124$^{\circ}$E∼127$^{\circ}$E) of Korean peninsula for 11 years (1999∼2000) have been compiled. The analysis method of numerical D/B is proposed and discussed its usability.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.34.2-34.2
• /
• 2019

Several observational results show a tighter pitch angle at wavelengths of optical and near-infrared than those that are associated with star formation, which is in agreement with the prediction of the density wave theory. In my recent numerical studies, the dependence of the shock positions relative to the potential minima is due to the tendency that stronger shocks form farther downstream. This causes a systematic variation of the perpendicular Mach number, with radius and makes the pitch angle of the gaseous arms smaller than that of the stellar arms, which supports the prediction of the density-wave theory, independently. However, some observations still give controversial results which show similar pitch angles at wavelengths, and there is no statistical study comparing observations and numerical models directly. By analyzing optical image of disk galaxies in the Carnegie-Irvine Galaxy Survey (CGS), I measured the physical values of stellar and gaseous arms such as their strength, length, and pitch angles. For direct comparison with numerical results, I analyzed more than 30 additional numerical models with varying the initial parameters in model galaxies. In this talk, I will present results both of observational and numerical samples and discuss the physical properties of spiral structures based on the density-wave theory.

• Transactions of Materials Processing
• /
• v.31 no.5
• /
• pp.296-301
• /
• 2022

In this study, influence of the process parameters of the roller leveling process on the straightness of the steel wire was analyzed using numerical analysis. To construct the numerical analysis model, cross-sectional and longitudinal element sizes, which affect the prediction accuracy of longitudinal stress caused by bending deformation of the steel wire, were optimized, and mass scaling that satisfies prediction accuracy while reducing computational time was confirmed. By using the constructed numerical analysis model, the influence of various process parameters such as input direction of the steel wire, initial diameter of the steel wire, back tension and intermesh on the straightness was confirmed. The simulation result shows that the 3^rd and 4^th roller of vertical straightener had a significant influence on vertical shape of the steel wire.

• Journal of Navigation and Port Research
• /
• v.37 no.1
• /
• pp.1-7
• /
• 2013

In this paper the developed prediction technique of wave-making resistance performance for a ship attached with a vertical blade had been verified. Numerical analysis program as a prediction technique had been developed using the Rankine source panel method and the vortex lattice method(VLM). The nonlinearity of the free surface conditions was fully taken into account using the iterative method and the trim and the sinkage of the ship were also considered in the numerical analysis program. Panel cutting method was applied to get hull surface panels. Numerical computations were carried out for a 4000TEU container carrier and the vertical blade was attached 6 different locations astern. To investigate the validity of the numerical analysis program the commercial viscous flow field analysis program FLUENT was used to obtain the viscous flow field around the ship and the model test was performed. The model test results were compared with the numerical analysis results.

• Journal of Industrial Technology
• /
• v.17
• /
• pp.277-289
• /
• 1997

The numerical model for prediction of longshore current with set-up/down effect on a plane beach is developed using the longshore component of the depth-integrated momentum balance equation. To predict the longshore current, the wave height model should first be formulated because the longshore current depends on the wave height directly. Two wave model, regular wave model and random wave model, are developed based on the energy flux balance equation. Also, the numerical model estimating the set-up inside the shoreline is developed using both the on-offshore momentum equation and the moving boundary technique. The numerical models are verified by the analytical solution, and compared with laboratory data. It is found from the comparison that developed models may be predicted accurately the longshore current with set-up/down effect on a plane beach.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.618-623
• /
• 2001

The transport of charged particles in electrostatic precipitator is investigated by Eulerian numerical analysis. Collection efficiencies are calculated using various combinations of the assumptions about flow field, turbulent diffusivity and boundary condition at collecting electrode. The characteristics of calculated collection efficiencies are compared with the trends of published experimental results. It is found that the collection efficiency for the case using nonuniform turbulent flow field, nonuniform turbulent diffusivity and zero concentration boundary condition at collecting electrode is the most suitable for the prediction of collection efficiency of electrostatic precipitator.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.2
• /
• pp.224-232
• /
• 2000

Four turbulent $k-{\varepsilon}$ models (i.e., standard model, modified models with streamline curvature modification and/or preferential dissipation modification) are applied in order to analyze the turbulent flow of wall-attaching offset jet. For numerical convergence, this paper develops a method of slowly increasing the convective effect induced by skew-velocity in skew-upwind scheme (hereafter called Partial Skewupwind Scheme). Even though the method was simple, it was efficient in view of convergent speed, computer memory storage, programming, etc. The numerical results of all models show good prediction in first order calculations (i.e., reattachment length, mean velocity, pressure), while they show some deviations in ·second order (i.e., kinetic energy and its dissipation rate). Like the previous results obtained by upwind scheme, the streamline curvature modification results in better prediction, while the preferential dissipation modification does not.

• Journal of the Korean Society of Combustion
• /
• v.4 no.1
• /
• pp.141-153
• /
• 1999

Numerical analysis for the combustion flow in the combustion chamber of incineration system has been carried out in order to acquire the basic design capability of incineration system. Established mathematical model was applied to the performance prediction of the pre-designed combustion chamber of commercial plant. Especially, combustion characteristics and the variation of flow pattern have been deeply discussed in accordance with secondary air injection. Secondary air injection was effective for the turbulent mixing between air and carbon monoxide/volatile matter resulting in considerably reduced CO content at the exit. Secondary air injection was found to be one of the key design parameters because the size of recirculation zone could be changed with the variation of injection characteristics.

• Journal of Bio-Environment Control
• /
• v.2 no.2
• /
• pp.99-109
• /
• 1993

Cooling of nutrient solution is essential to improve the growth environment of crops in hydroponic culture during summer season in Korea. This study was carried out to provide fundamental data for development of the cooling system satisfying the required cooling load of nutrient solution in hydroponic greenhouse. A numerical model for prediction of the cooling load of nutrient solution in hydroponic greenhouse was developed, and the results by the model showed good agreements with those by experiments. Main factors effecting on cooling load were solar radiation and air temperature in weather data, and conductivity of planting board and area ratio of bed to floor in greenhouse parameters. Using the model developed, the design cooling load of nutrient solution in hydroponic greenhouse of 1,000$m^2$(300pyong) was predicted to be 95,000 kJ/hr in Suwon and the vicinity.