• Title/Summary/Keyword: Two-dimensional numerical model

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A Three-Dimensional Turbulence Model far the Thermal Discharge into Cross-Flow Field (가로흐름 수역으로 방출되는 3차원 온배수 난류모형)

  • 이남주;최흥식;허재영
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.7 no.2
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    • pp.148-155
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    • 1995
  • For an accurate prediction of the temperature Held induced by surface discharge of heated water into an ambient cross-flow field. a three-dimensional near-field numerical model using k-$\varepsilon$ turbulence clousure is developed Rather restricted as it is, the numerical results of the model agree well with the experimental data. The developed model simulates quite adequately the stratification, gravitational lateral spreading, and upward entrainment of thermal jet which cannot be simulated by a depth-integrated two-dimensional numerical model, as well as the interaction with cross-flow.

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An Analysis of Drainage Characteristics at Large-Sized Paddy Fields Using a Two-Dimensional Numerical Model (2차원 유한체적 수치모형을 이용한 대구획 논의 배수특성 분석)

  • Park, Seung-Woo;Park, Jong-Min;Kang, Min-Goo
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.3
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    • pp.3-14
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    • 2004
  • A two-dimensional numerical model based on a finite volume method was formulated to solve the shallow water equations and applied for evaluating drainage characteristics at large-sized paddy fields. Manning roughness coefficient was calibrated using the observed inundating depths at drainage tests, and used for validating the model with the results from another drainage test. The simulated results were in good agreement with the observed inundating depths. The result of surface drainage showed that the longer width of the outlet was or the more the number of drainage outlet was, the shorter the drainage time was taken, and the larger the size of the field become, the longer the drainage time was taken, and the field shape had little effect on drainage time. To reduce the drainage time to 24 hours, the outlet is located lower than the elevation of the basin and small drainage ditch is constructed at the field. The results showed that the drainage time was taken short as the small drainage ditch was constructed. The comparison of drainage time as to the size of field constructed small drainage ditch showed the field, 100m ${\times}$ 200 m, can be drained in 24 hours.

Three-Dimensional Visualization of Flood Inundation for Local Inundation Map (홍수지도 제작을 위한 홍수범람정보의 3차원 가시화)

  • Lee, Jin-Woo;Kim, Hyung-Jun;Cho, Yong-Sik
    • 한국방재학회:학술대회논문집
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    • 2008.02a
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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.

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TWO-DIMENSIONAL CAVITATION PREDICTION BASED ON APPROXIMATE JACOBIAN MATRIX IN TWO-FLUID TWO-PHASE FLOW MODELS (2-유체 2상-유동 모델에서 근사 Jacobian 행렬을 이용한 2차원 캐비테이션의 예측)

  • Yeom Geum-Su;Chang Keun-Shik
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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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.

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Development of a New Simulation Method of Casting Process Based on a Cylindrical Coordinate System (원통좌표를 이용한 주조공정의 수치해석모델 개발)

  • Mok, Jin-Ho;Park, Seong-Joon;Lee, Jin-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.4
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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.

Three dimensional flow analysis within a profile extrusion die by using control volume finite-element method

  • Kim, Jongman;Youn, Jae-Ryoun;Hyun, Jae-Chun
    • Korea-Australia Rheology Journal
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    • v.13 no.2
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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.

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Comparison between a 3 Dimensional Turbulent Numerical Model and Hydraulic Experiment Model for the flow phenomenon around a Lock Gate (배수갑문 주위의 흐름현상에 대한 3차원 난류 수치모형과 수리모형실험의 비교)

  • Lee, Sang-Hwa;Jang, Eun-Cheul;Ha, Jae-Yul
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.19 no.2
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    • pp.162-169
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    • 2007
  • This study is focused on the comparison of a 3 dimensional numerical and hydraulic model experiment for the flow phenomenon when a lock gate is opened. The lock gate is designed to discharge the flood flow rate at $218m^3/s$ of Solicheon at the Kun Jang national industry complex. The three dimensional ${\kappa}-{\epsilon}$ turbulent model of ANSYS CFX-10 of the computational fluid dynamics(CFD) program was used. The characteristics of CFX-10 are able to be simulated effectively for turbulent flow, especially the flow separation of the boundary layer of the two phase interface of air and water. The velocity and the flow pattern of the numerical model was showed to be similar to the results of the hydraulic model experiment.

A Study on the Development of a Three Dimensional Numerical Model for the Casting Processes (주조공정의 수치해석을 위한 3차원 전산모델 개발에 관한 연구)

  • ;S.Patankar
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.10
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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.

Numerical Simulation of Wave Deformation due to a Submerged Structure with a Second-order VOF Method (2차 정확도 VOF기법을 활용한 수중구조물에 의한 파랑변화 예측)

  • Ha, Tae-Min;Cho, Yong-Sik
    • Journal of the Korean Society of Hazard Mitigation
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    • v.10 no.1
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    • pp.111-117
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    • 2010
  • A three-dimensional numerical model is employed to investigate wave deformation due to a submerged structure. The three-dimensional numerical model solves the spatially averaged Navier-Stokes equations for two-phase flows. The LES(large-eddy-simulation) approach is adopted to model the turbulence effect by using the Smagorinsky SGS(sub-grid scale) closure model. The two-step projection method is employed in the numerical solutions, aided by the Bi-CGSTAB technique to solve the pressure Poisson equation for the filtered pressure field. The second-order accurate VOF(volume-of-fluid) method is used to track the distorted and broken free surface. A simple linear wave is generated on a constant depth and compared with analytical solutions. The model is then applied to study wave deformation due to a submerged structure and the predicted results are compared with available laboratory measurements.

A Study on Numerical Analysis for 2 Dimensional Circulation Model with Effect of Nonlinear Term (비선형항의 효과를 고려한 2차원 유동모형에 대한 수치해석연구)

  • 김희종;김진후;이상화
    • Journal of Ocean Engineering and Technology
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    • v.4 no.1
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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.

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