• 한국건축시공학회지
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• 제19권1호
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• pp.39-46
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• 2019

본 연구에서는 비압축성 Navier-Stokes 방정식을 적용한 ISPH 기법을 이용하여 3차원 유동 수치해석 모델을 개발하였다. 수치해석을 위해 MATLAB을 사용하여 ISPH 프로그램을 구현하였다. ISPH의 커널 함수로 piecewise cubic spline 함수를 사용하였다. 벽 경계조건으로 고정 가상 입자를 사용하였으며, 가상 밀도를 적용하여 자유 표면 경계 부근의 입자들을 결정하였다. 수치해석 모델과 코드의 정도를 확인하기 위해 $T_{500}$ 시험, 슬럼프 플로우 시험, L-box 시험의 수치해석 결과와 실험 결과를 비교하였다. 수치해석 결과 고유동 콘크리트의 점성계수 및 항복응력 변화에 따른 유동 현상의 특성을 잘 묘사하였으며, 기존의 실험값과 비교적 잘 일치함을 확인할 수 있었다.

• 천문학회지
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• 제47권3호
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• pp.87-98
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• 2014

We develop a parallel cosmological hydrodynamic simulation code designed for the study of formation and evolution of cosmological structures. The gravitational force is calculated using the TreePM method and the hydrodynamics is implemented based on the smoothed particle hydrodynamics. The initial displacement and velocity of simulation particles are calculated according to second-order Lagrangian perturbation theory using the power spectra of dark matter and baryonic matter. The initial background temperature is given by Recfast and the temperature uctuations at the initial particle position are assigned according to the adiabatic model. We use a time-limiter scheme over the individual time steps to capture shock-fronts and to ease the time-step tension between the shock and preshock particles. We also include the astrophysical gas processes of radiative heating/cooling, star formation, metal enrichment, and supernova feedback. We test the code in several standard cases such as one-dimensional Riemann problems, Kelvin-Helmholtz, and Sedov blast wave instability. Star formation on the galactic disk is investigated to check whether the Schmidt-Kennicutt relation is properly recovered. We also study global star formation history at different simulation resolutions and compare them with observations.

• 천문학회지
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• 제34권4호
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• pp.209-213
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• 2001

This paper describes the numerical solution to the hyperbolic system of magnetohydrodynamic (MHD) equations. First, by pointing out the approximations involved, the deal MHD equations are presented. Next, the MHD waves as well as the associated shocks and discontinuities, are presented. Then, based on the hyperbolicity of the ideal MHD equations, the application of upwind schemes, which have been developed for hydrodynamics, is discussed to solve the equations numerically. As an definite example, one and multi-dimensional codes based on the Total Variation Diminishing scheme are presented. The treatment in the multi-dimensional code, which maintains ${\nabla}{\cdot}$B = 0, is described. Through tests, the robustness of the upwind schemes for MHDs is demonstrated.

• 천문학회보
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• 제32권1호
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• pp.43.1-43.1
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• 2007

• 천문학회지
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• 제34권4호
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• pp.271-273
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• 2001

We present a 4-parameter implicit Lagrangean code which satisfies conservation of mass, linear and angular momenta, energy and entropy simultaneously. The primary advantage of this scheme is possibility to control dissipative properties of the scheme avoiding the effects of numerical viscosity.

• 한국기계가공학회지
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• 제16권3호
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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.

• 한국물환경학회지
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• 제28권3호
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• pp.384-393
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• 2012

Saemangeum lake is an artificial lake created by reclamation works and an estuary embankment since 2006. The sea water flows into the lake by the operation of two sluice gates, and the freshwater enters into the lake by the upper streams. For the reflection of hydrology and hydrodynamics effects in Saemangeum area, a hydrodynamics model was developed by connecting Hydrological Simulation Program with Fortran (HSPF) and Environmental Fluid Dynamic Code (EFDC). The HSPF was applied to simulate the freshwater discharge from the upper steam watershed, and the EFDC was performed to compute water flow, water temperature, and salinity based on time series from 2008 to 2009. The calibration and validation are performed to analyze horizontal and vertical gradients. The horizontal trend of model simulation results is reflected in the trend of observed data tolerably. The vertical trend is conducted an analysis of seasonal comparisons because of the limitation of vertically observed data. Water temperature reflects on the seasonal changes. Salinity has an effect on the near river input spots. The impact area of salinity is depending on the sea water distribution by gate operation, mainly.

• 한국터널지하공간학회 논문집
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• 제15권3호
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• pp.345-356
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• 2013

본 연구에서는 SPH(Smoothed Particle Hydrodynamics) 코드를 사용하여 TBM에 장착되는 디스크커터에 의한 암석의 절삭과정을 모사하였다. 이를 위하여 본 연구에서는 3차원 FEM 해석 상용프로그램인 AUTODYN3D를 사용하였으며 이를 통해 국내 황등화강암을 대상으로 총 25개의 절삭조건에 대한 수치적인 절삭시험을 수행하였다. 암석과 디스크커터를 각각 라그란지안 솔버와 SPH 솔버를 사용하여 3차원 형상으로 모델링 하고 두 개의 디스크커터가 순차적으로 암석을 절삭하도록 모델링 하였다. 수치해석과 LCM시험에서 측정한 디스크커터의 작용력은 오차 10%이내의 값을 보여 대체로 일치하는 것으로 나타났고 균열의 전파양상과 암석의 파쇄양상 또한 유사한 것으로 나타났다. 또한 절삭된 최적 커터간격을 측정한 결과 LCM시험 결과와 일치하였다. 이를 통해 SPH코드를 사용한 수치해석기법의 적용성을 확인할 수 있었으나 해석시간을 단축하기 위한 Lagrange-SPH코드의 커플링에 관한 후속연구가 필요할 것으로 판단되었다.

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.31-37
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• 2005

An attempt to improve the speed performance through the minimizing in wave resistance has been done by an application of gooseneck and no bulb type to bulbous bow for the DSME 78,500 Class LPG Carrier on the basis of the CFD calculation and comparatives model tests. The hydrodynamic characteristics according to the variation of the shape of Cp-curve, design load water line, frame line and bulbous bow that have an important effect on the wave resistance has been evaluated/calculated by ship-flow code. A wide variety in hull variation have been tried to have a good hull form with three types of fore-body hull forms mainly classified by the shape of bulbous bow. The speed performances for the three final hull forms with different bulbous bows have been evaluated through the model tests.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3367-3382
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• 2023

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian computational fluid dynamics method that has been widely used in the analysis of physical phenomena characterized by large deformation or multi-phase flow analysis, including free surface. Despite the recent implementation of eddy-viscosity models in SPH methodology, sophisticated turbulent analysis using Lagrangian methodology has been limited due to the lack of computational performance and numerical consistency. In this study, we implement the standard and dynamic Smagorinsky model and dynamic Vreman model as sub-particle scale models based on a weakly compressible SPH solver. The large eddy simulation method is numerically identical to the spatial discretization method of smoothed particle dynamics, enabling the intuitive implementation of the turbulence model. Furthermore, there is no additional filtering process required for physical variables since the sub-grid scale filtering is inherently processed in the kernel interpolation. We simulate lid-driven flow under transition and turbulent conditions as a benchmark. The simulation results show that the dynamic Vreman model produces consistent results with experimental and numerical research regarding Reynolds averaged physical quantities and flow structure. Spectral analysis also confirms that it is possible to analyze turbulent eddies with a smaller length scale using the dynamic Vreman model with the same particle size.