• Coupled systems mechanics
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• 제8권4호
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• pp.339-350
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• 2019

A numerical simulation of the incompressible multiphase hydraulic jump flow was performed to compare the interface prediction through the use of the three RANS turbulence models: $k-{\varepsilon}$, $RNGk-{\varepsilon}$ and SST $k-{\omega}$. A three dimensional no submerged hydraulic jump and a two dimensional submerged hydraulic jump were modeled. Both the geometry and the mesh were created using the open source Gmsh code. The project's geometry consists of a rectangular channel with length and height differences between the two dimensional and three dimensional simulations. Uniform hexahedral cells were used for the mesh. Three refining meshes were constructed to allow to verify simulation convergence. The Volume of Fluid (abbr. VOF) method was used for treatment of the air-water surface. The turbulence models were evaluated in three distinct set up configurations to provide a greater accuracy in the flow representation. In the two-dimensional analysis of a submerged hydraulic jump simulation, the turbulence model RNG RNG $k-{\varepsilon}$ provided a better interface adjust with the experimental results than the model $k-{\varepsilon}$ and SST $k-{\omega}$. In the three-dimensional simulation of a no-submerged hydraulic jump the k-# showed better results than the SST $k-{\omega}$ and RNG $k-{\varepsilon}$ capturing the height and length of the ledge with a better fit with the experimental results.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1987년도 제29회 수공학연구발표회논문초록집
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• pp.113-122
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• 1987

A numerical simulation technique of three-dimensional finite difference model is developed to study the groundwater flow system in Dcjima, an upland area which faces Kasumigaura Lake. For general perspectives of the groundwater flow system, a steady state three-dimentional model is simulated. For the sedimentary mud formations which are found in the representative formation, three situations of hydraulic conductivity are considered, representing an isotropic condition and situations where the horizontal permeability is equal to 10 times and 100times of the vertical one. The finite difference grid used in the simulation has 60x50x30=90,000 nodes. A converged solution with a tolerance of 0.001 meter of hydraulic head is set. Having determined the flow net by using a steady state three-dimensional model. the results for the three cases of hydraulic conductivity are compared with the results of tracer methods (Bae and Kayane 1987) With the aid of four representative vertical cross-sections, groundwater flow systems in the study area are assumed. Water balances for the three cases indicate very good agreement between total recharge and discharge in each case Analyses of groundwater flow system based on the tritium concentrations and water quality measurements (Bae and Kayane 1987) are confirmed by the numerical simulation and the results obtained by these two methods appeared to be in close agreement.

• Nuclear Engineering and Technology
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• 제44권6호
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• pp.639-652
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• 2012

A three-dimensional discrete fracture network model was developed in order to simulate the hydraulic characteristics of a granitic rock mass at Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT). The model used a three-dimensional discrete fracture network (DFN), assuming a correlation between the length and aperture of the fractures, and a trapezoid flow path in the fractures. These assumptions that previous studies have not considered could make the developed model more practical and reasonable. The geologic and hydraulic data of the fractures were obtained in the rock mass at the KURT. Then, these data were applied to the developed fracture discrete network model. The model was applied in estimating the representative elementary volume (REV), the equivalent hydraulic conductivity tensors, and the amount of groundwater inflow into the tunnel. The developed discrete fracture network model can determine the REV size for the rock mass with respect to the hydraulic behavior and estimate the groundwater flow into the tunnel at the KURT. Therefore, the assumptions that the fracture length is correlated to the fracture aperture and the flow in a fracture occurs in a trapezoid shape appear to be effective in the DFN analysis used to estimate the hydraulic behavior of the fractured rock mass.

• Computers and Concrete
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• 제15권1호
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• pp.103-126
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• 2015

Thermal effects are significant loads for assessing concrete dam behaviour during operation. A new methodology to estimate thermal loads on concrete dams taking into account processes which were previously unconsidered, such as: the evaporative cooling, the night radiating cooling or the shades, has been recently reported. The application of this novel approach in combination with a three-dimensional finite element method to solve the heat diffusion equation led to a precise characterization of the thermal field inside the dam. However, that approach may be computationally expensive. This paper proposes the use of a new one-dimensional model based on an explicit finite difference scheme which is improved by means of the reported methodology for computing the heat fluxes through the dam faces. The improved model has been applied to a case study where observations from 21 concrete thermometers and data of climatic variables were available. The results are compared with those from: (a) the original one-dimensional finite difference model, (b) the Stucky-Derron classical one-dimensional analytical solution, and (c) a three-dimensional finite element method. The results of the improved model match well with the observed temperatures, in addition they are similar to those obtained with (c) except in the vicinity of the abutments, although this later is a considerably more complex methodology. The improved model have a better performance than the models (a) and (b), whose results present larger error and bias when compared with the recorded data.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(1)
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• pp.145-146
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• 2005

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.405-411
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• 2000

This study reviews qualitatively the flow characteristics around th tidal gap during seadike closures using a three-dimensional model for shallow water equations. The Princeton Ocean Model(POM) was adapted and applied to the Sihwa Seadike which was closed in 1994. The simulated flow patterns around the gap showed that tidal velocities increase with the cross-sectional area during ebb tide. The accelerated flow extended to wider zones passing the gap, and shock waves were generated. Vertical tidal velocity profiles were affected as the bottom scours developed beyond normal conditions.

• 한국해안해양공학회지
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• 제19권2호
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• pp.162-169
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• 2007

본 연구는 갑문 개방시 유출부의 흐름 현상을 수리모형실헐 결과와 3차원 수치모형실험을 비교 분석하는데 역점을 두고 있다. 대상 갑문은 군장(군산-장항)국가산업단지내의 솔리천에서 유입되는 홍수량 $218m^3/s$을 배제하기 위해서 설계된 배수갑문이다. 수치실험에 사용된 모형은 상용 전산유체역학 프로그램인 ANSYS CFX-10의 ${\kappa}-{\epsilon}$ 난류모형이다. CFX-10의 장점은 난류 흐름에 대해 현상을 양호하게 시뮬레이션 할 수 있으며 특히 물과 공기 접촉면(two phase interface)인 경계층에서 흐름 분리현상을 비교적 뚜렷하게 해석할 수 있다. 수치실험에서 해석된 유속 및 수면의 흐름 형태는 수리모형실험과 유사하게 나타났다.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1347-1360
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• 2009

A multi-dimensional component for the thermal-hydraulic system analysis code, MARS, was developed for a more realistic three-dimensional analysis of nuclear systems. A three-dimensional and two-fluid model for a two-phase flow in Cartesian and cylindrical coordinates was employed. The governing equations and physical constitutive relationships were extended from those of a one-dimensional version. The numerical solution method adopted a semi-implicit and finite-difference method based on a staggered-grid mesh and a donor-cell scheme. The relevant length scale was very coarse compared to commercial computational fluid dynamics tools. Thus a simple Prandtl's mixing length turbulence model was applied to interpret the turbulent induced momentum and energy diffusivity. Non drag interfacial forces were not considered as in the general nuclear system codes. Several conceptual cases with analytic solutions were chosen and analyzed to assess the fundamental terms. RPI air-water and UPTF 7 tests were simulated and compared to the experimental data. The simulation results for the RPI air-water two-phase flow experiment showed good agreement with the measured void fraction. The simulation results for the UPTF downcomer test 7 were compared to the experiment data and the results from other multi-dimensional system codes for the ECC delivery flow.

• Computers and Concrete
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• 제19권5호
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• pp.527-535
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• 2017

In this study, an aging deformation statistical model for a unique high and steep rock slope was proposed, and the aging characteristic of the slope deformation was better reflected. The slope displacement was affected by multiple-environmental factors in multiple scales and displayed the same tendency with a rising water level. The statistical model of the high and steep rock including non-aging factors was set up based on previous analyses and the study of the deformation and residual tendency. The rule and importance of the water level factor as a non-aging unit was analyzed. A partitioned statistical model and mutation model were established for the comprehensive cumulative displacement velocity with the monitoring study under multiple factors and multiple parameters. A spatial model was also developed to reflect and predict the whole and sectional deformation character by combining aging, deformation and space coordinates. A neural network model was built to fit and predict the deformation with a high degree of precision by mastering its feature of complexity and randomness. A three-dimensional finite element model of the slope was applied to approach the structure character using numerical simulations. Further, a three-dimensional finite element model of the slope and dam was developed, and the whole deformation state was analyzed. This study is expected to provide a powerful and systematic method to analyze very high, important and dangerous slopes.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1726-1731
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• 2006

본 연구에서는 임하다목적댐의 비상여수로 설계를 위하여 수리모형실험과 수치모형실험을 수행하였다. 수치모의에는 3차원 수치모형인 FLOW-3D를 사용하였다. 비상여수로 설계를 위하여 접근수로부, 월류웨어부, 천이부 및 도류부, 그리고 감세부로 나누어 수리모형실험과 수치모형실험의 수리현상 결과를 비교하였다. 최적의 비상여수로 설계를 위하여 기본계획안에 대하여 모의하고 이에 대한 보완점과 문제점들을 찾아내고 해결책을 제시하였다. 수치모의를 통하여 수리모형실험에서 쉽게 수행하기 어려운 다양한 조건을 모의하고 최적의 결과에 찾아 이를 수리모형실험으로 검증함으로써 비상여수로 기본설계안을 도출하였다.