• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.179-182
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• 2008

This study simulated the flood inundations of the Nakdong River catchment running through Yangsan, a small city located in the south eastern area of Korea by using the depth averaged two-dimensional hydrodynamic numerical model. The numerical model employs the staggered grid system including moving boundary and a finite different method to solve the Saint-Venant equations. A second order upwind scheme is used to discretize the nonlinear convection terms of the momentum equations, whereas linear terms are discretized by a first order leap-frog scheme(Cho and Yoon, 1998). The numerical model was applied to a real topography to simulate the flood inundation of the Yangsan basin. The numerical results for urban district are visualized in three dimension. These results can be essentially utilized to construct the three dimensional inundation map after building the GIS-based database in local public organizations in order to protect the life and property safely.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.183-186
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• 2005

We developed an upwind numerical formulation based on the eigenvalues of the approximate Jacobian matrix in order to solve the hyperbolic conservation laws governing the two-fluid two-phase flow models. We obtained eight analytic eigenvalues in the two dimensions that can be used for estimate of the wave speeds essential in constructing an upwind numerical method. Two-dimensional underwater cavitation in a flow past structural shapes or by underwater explosion can be solved using this method. We present quantitative prediction of cavitation for the water tunnel wall and airfoils that has both experimental data as well as numerical results by other numerical methods and models.

• 대한기계학회논문집B
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• 제28권4호
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• pp.433-440
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• 2004

Since the numerical analysis was adopted in the mold design, lots of computational methods have been proposed for the simulations of casting processes for the various shaped molds. Today, it is possible to simulate the filling and solidification processes of most casts using the VOF technique. Though the three-dimensional numerical model based on the Cartesian coordinate system can be applied to any shape of cast, it becomes very inefficient when the three-dimensional model is applied to the cast of axi-symmetrical shape since the control volume includes at least 11 of the physical model. In addition, the more meshes should be distributed along the circumferential boundaries of curved shape in the Cartesian coordinate system fur the better results, while such curved circumferential boundary does not need to be considered in the two-dimensional cylindrical coordinate system. This motivates the present study i.e. developing a two-dimensional numerical model for the axi-symmetrically shaped casts. The SIMPLER algorithm, the VOF method, and the equivalent specific heat method have been adopted in the combined algorithm for the flow calculation, the free surface tracking, and the phase change heat transfer, respectively. The numerical model has been applied to the casting process of a pulley, and it was proven that the mesh and time effective calculation was accomplished comparing to the calculation using three-dimensional model.

• Korea-Australia Rheology Journal
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• 제13권2호
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• pp.97-106
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• 2001

Three-dimensional flow analysis was performed by using the control volume finite-element method for design of a profile extrusion die. Because polymer melt behavior is complicated and cross-sectional shape of the profile extrusion die is changing continuously, the fluid flow within the die must be analyzed three-dimensionally. A commercially available polypropylene is used for theoretical and experimental investigations. Material properties are assumed to be constant except for the viscosity. The 5-constant modified Cross model is used for the numerical analysis. A test problem is examined in order to verify the accuracy of the numerical method. Simulations are performed for conditions of three different screw speeds and three different die temperatures. Predicted pressure distribution is compared with the experimental measurements and the results of the previous two-dimensional study. The computational results obtained by using three dimensional CVFEM agree with the experimental measurements and are more accurate than those obtained by using the two-dimensional cross-sectional method. The velocity profiles and the temperature distributions within several cross-sections of the die are given as contour plots.

• 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.

• 대한기계학회논문집B
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• 제26권10호
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• pp.1436-1444
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• 2002

A three dimensional numerical model was developed to analyze the mold filling and solidification processes straightforwardly in a casting processes. On the basis of the SIMPLER algorithm, the VOF method and the Equivalent Specific Heat method were adopted to deal with the free surface behavior and the latent heat evolution. The complete model has been validated using exact solutions and experimental results. The importance of three-dimensional effects has been highlighted by comparing the results from the three-dimensional analysis with those given by a two-dimensional analysis.

• 한국방재학회 논문집
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• 제10권1호
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• pp.111-117
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• 2010

수중구조물에 의한 파랑의 변형을 예측하기 위해 3차원 수치모형을 도입하여 수치모형 실험을 수행하였다. 본 수치모형은 Navier-Stokes 방정식을 유한차분법을 이용하여 계산하는 동수압 모형으로서, 난류의 해석을 위해서 상대적으로 큰 에디(eddy)만을 고려하는 SANS(Spatially Averaged Navier-Stokes) 방정식의 해를 구하는 LES(large-eddy-simulation) 기반의 수치모형이다. 엇갈림 격자체계에서 유한차분법을 사용하여 지배방정식을 해석하는 모형으로서 수치기법으로 Two-step projection 기법을 사용하여 SANS 방정식을 계산하였으며, Bi-CGSTAB 기법을 이용하여 Poisson 방정식의 해를 구하고 압력장을 계산하였다. 또한, 자유수면의 추적을 위하여 2차 정확도의 VOF(volume-of-fluid) 기법을 사용하였다. 먼저 선형파를 일정 수심상에서 조파시켜 해석해와 비교한 후 수중구조물이 설치된 지형에 적용하여 파랑의 변형을 수치모의하여 수리모형 실험결과와 비교 및 분석하였다.

• 한국해양공학회지
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• 제4권1호
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• pp.49-54
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• 1990

This study describes the application of a two dimensional depth integrated numerical model. The explict scheme of finite difference method had been applied to the model of circulation. The nonlinear terms showed a slight difference for the variations of water elevation when calculated grid was small. They were also found to be minor when calculated grid size was increased. For verification of the numerical model, numerical results were compared with predicted values and field data. In the model, the effect of nonlinear advective terms proved not to be significant.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.155-158
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• 2008

A practical modeling approach of a small slinger combustor is proposed and a 2-dimensional axisymmetric computational model is developed. Based on numerical results from the full 3-dimensional configuration, model reduction is achieved toward 2-dimensional axisymmetric configuration. By simplifying the complex model, computing time can be significantly reduced and it makes easy to find effects of geometry modification. Numerical results show that the flow characteristic of 2-D model is quite similar to that of the 3-D configuration.

• Journal of Welding and Joining
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• 제15권4호
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• pp.63-69
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• 1997

Welding distortion is more serious problem than any other problems caused by welding process, especially, in the heavy-industrial place. These welding distortions are caused by nonuniform heating and cooling of metal during and after welding operations. And these distortion quantities are must be known to worker in production line because distorions are important role in assembling part. Therefore an analytical model to explain and predict the welding distortion are needed. A numerical analysis of welding distortion which is inelastic behavior of weldment would require the three dimensional calculation. But computing time and memory would be very large, and the resulting cost might be unacceptable. Therefore we use a numerical technique for two dimensional analysis in the section normal to the weld direction of weldment under an assumption of quasi-stationary conditions. But the result of the calculation under two dimensional(plane strain) assumption was not satisfied as compared with experimental result. This paper proposed a technique for analysing the welding angular distortion by using a constraint boundary condition on the two dimensional finite element model. The simulation results revealed that the constraint boundary model could more reasonably describe the welding distortion than the plane strain model did.