• Coupled systems mechanics
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• v.10 no.6
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• pp.491-507
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• 2021

The aim of this paper is to conduct a hydrodynamic analysis of fluid flow over different weir types using the analytical solution, the physical model taken from another article, and numericalsimulations through the Smoothed particle hydrodynamic method (SPH) using the compiled DualSPHysics source code. The paper covers the field of real fluid dynamics that includes a description of different proposed types of weirs in various flow regimes and the optimal solution for the most efficiency structure shape. A detailed presentation of the method, the structure and it's characteristics are included. Apart from the single stepped weir, two other weir types are proposed: a Divided type and a Downstream slopped type. All of them are modeled using the SPH method.

• Journal of the Korean Society of Visualization
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• v.16 no.1
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• pp.54-60
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• 2018

It is important to develop more efficient and productive casting processes for an automated high precision molten-metal casting system. Detailed analysis of molten-metal flow in the casting process by the numerical approach will help to optimize the control of a ladle. In this study, the smoothed particle hydrodynamics method was applied to analyze casting flow characteristics with different tilting angular speed and initial molten-metal level. The smoothed particle hydrodynamics technique has advantages to easily handle non-linear free surface behavior with the absence of a computational mesh. We found that tilting angular speed has relatively greater effect on the casting flowrate and that the effect of the initial molten-metal level is only minor. Further extensive study will be necessary to find an optimal condition for high efficient casting system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.94-99
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• 2017

The buoy of the wave energy converter moves by direct contact with the fluid. In order to design a buoy by using the numerical method, it is necessary to analyze not only the contact with the fluid but also the exact behavior of the fluid. In this paper, differences between weakly compressible smoothed particle hydrodynamics (WCSPH) and incompressible smoothed particle hydrodynamics (ISPH) are compared and analyzed for two-dimensional dam breaking simulation. ABAQUS, which is a commercial analysis program, is used for WCSPH analysis. A laboratory code is developed for ISPH analysis. The surface shape, the velocity, and the pressure pattern of the fluid are compared. The results of the laboratory code show the similar tendencies with those of ABAQUS, and there is a little difference in the pressure result.

• Journal of The Korean Astronomical Society
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• v.33 no.1
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• pp.1-17
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• 2000

We have performed extensive simulations of response of gaseous disk in barred galaxies using SPH method. The gravitational potential is assumed to be generated by disk, bulge, halo, and bar. The mass of gaseous disk in SPH simulation is assumed to be negligible compared to the stellar and dark mass component, and the gravitational potential generated by other components is fixed in time. The self-gravity of the gas is not considered in most simulations, but we have made a small set of simulations including the self-gravity of the gas. Non-circular component of velocity generated by the rotating, non-axisymmetric potential causes many interesting features. In most cases, there is a strong tendency of concentration of gas toward the central parts of the galaxy. The morphology of the gas becomes quite complex, but the general behavior can be understood in terms of simple linear approximations: the locations and number of Lindblad resonances play critical role in determining the general distribution of the gas. We present our results in the form of 'atlas' of artificial galaxies. We also make a brief comment on the observational implications of our calculations. Since the gaseous component show interesting features while the stellar component behaves more smoothly, high resolution mapping using molecular emission line for barred galaxies would be desirable.

• Atmosphere
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• v.33 no.4
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• pp.387-398
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• 2023

The double Fourier series (DFS) spectral dynamical core is evaluated for the two idealized test cases in comparison with the spherical harmonics (SPH) spectral dynamical core. A new approach in calculating the meridional expansion coefficients of DFS, which was recently developed to alleviate a computational error but only applied to the 2D spherical shallow water equation, is also tested. In the 3D deformational tracer transport test, the difference is not conspicuous between SPH and DFS simulations, with a slight outperformance of the new DFS approach in terms of undershooting problem. In the baroclinic wave development test, the DFS-simulated wave pattern is quantitatively similar to the SPH-simulated one at high resolutions, but with a substantially lower computational cost. The new DFS approach does not offer a salient advantage compared to the original DFS while computation cost slightly increases. This result suggests that the current DFS spectral method can be a practical and alternative dynamical core for high-resolution global modeling.

• Journal of the Korea Computer Graphics Society
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• v.18 no.3
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• pp.17-27
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• 2012

In this paper, we describe a case study of the film 'Sector 7' which was produced by technologies applied fluid simulation. For the CG scenes in the movie which include highly detailed fluid motions, we used smoothed particle hydrodynamics(SPH) technique to express subtle movements of seawater from a crashed huge tank, and used hybrid simulation method of particles and levelsets to describe bursting water from a submarine's broken canopy. We also used detonation shock dynamics(DSD) technique for detailed flame simulations to produce a burning monster, the film"s main character. At this point, the divergence-free vortex particle method was applied to conserve the incompressible property of fluids. In addition, we used an upsampling method to achieve more efficient video production. Consequently, we could produce the high-quality visual effects by using the domestic technologies.

• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3543-3562
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• 2021

The methods and performance of a 3D pin-by-pin neutronics code based on the 2D/1D decoupling method are presented. The code was newly developed as an effort to achieve enhanced accuracy and high calculation performance that are sufficient for the use in practical nuclear design analyses. From the 3D diffusion-based finite difference method (FDM) formulation, decoupled planar formulations are established by treating pre-determined axial leakage as a source term. The decoupled axial problems are formulated with the radial leakage source term. To accelerate the pin-by-pin calculation, the two-level coarse mesh finite difference (CMFD) formulation, which consists of the multigroup node-wise CMFD and the two-group assembly-wise CMFD is implemented. To enhance the accuracy, both the discontinuity factor method and the super-homogenization (SPH) factor method are examined for pin-wise cross-section homogenization. The parallelization is achieved with the OpenMP package. The accuracy and performance of the pin-by-pin calculations are assessed with the VERA and APR1400 benchmark problems. It is demonstrated that pin-by-pin 2D/1D alternating calculations within the two-level 3D CMFD framework yield accurate solutions in about 30 s for the typical commercial core problems, on a parallel platform employing 32 threads.

• Ocean Systems Engineering
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• v.12 no.1
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• pp.63-86
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• 2022

A refined projection-based purely Lagrangian meshfree method is presented towards reliable numerical analysis of fluid flow interactions with saturated/unsaturated porous media of uniform/spatially-varying porosities. The governing equations are reformulated on the basis of two-phase mixture theory with incorporation of volume fraction. These principal equations of mixture are discretized in the context of Incompressible SPH (Smoothed Particle Hydrodynamics) method. Associated with the consideration of governing equations of mixture, a new term arises in the source term of PPE (Poisson Pressure Equation), resulting in modified source term. The linear and nonlinear force terms are included in momentum equation to represent the resistance from porous media. Volume increase of fluid particles are taken into consideration on account of the presence of porous media, and hence multi-resolution ISPH framework is also incorporated. The stability and accuracy of the proposed method are thoroughly examined by reproducing several numerical examples including the interactions between fluid flow and saturated/unsaturated porous media of uniform/spatially-varying porosities. The method shows continuous pressure field, smooth variations of particle volumes and regular distributions of particles at the interface between fluid and porous media.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.3
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• pp.329-347
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• 2018

The Smoothed Particle Hydrodynamics (SPH) method has proved to have great potentials in dealing with the wave-structure interactions. Compared with the Weakly Compressible SPH (WCSPH) method, the ISPH approach solves the pressure by using the pressure Poisson equation rather than the equation of state. This could provide a more stable and accurate pressure field that is important in the study of wave-structure interactions. This paper improves the solid boundary treatment of ISPH by using a high accuracy Simplified Finite Difference Interpolation (SFDI) scheme for the 2D wave-structure coupling problems, especially for free-moving structure. The proposed method is referred as the ISPH_BS. The model improvement is demonstrated by the documented benchmark tests and laboratory experiment covering various wave-structure interaction applications.

• Journal of the Korean Applied Science and Technology
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• v.5 no.2
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• pp.17-28
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• 1988

This experiment is carried out to study alteration of phospholipid compoent in liver, kidney, testis, and brain tissues of male rats which are fed selenium added high fat diets for 7 weeks. The phospholipids of these tissues are analyzed by TLC method. The results are as follows. 1. The growth rate and food intake levels are not affected by selenium-added high fat diets. 2. The levels of total cholesterol, total lipid and TBA are lower in selenium-added diets than selenium free diets 3. The total phospholipid levels of each tissue are kidney > brain > testis > liver and the levels of phospholipid component are Le>Sph>Ce>LLe for kidney and liver, Le>Sph>LLe>Ce for testis and brain.