• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.193-200
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• 1999

An unstructured implicit Euler solver is parallelized on a Cray T3E. Spatial discretization is accomplished by a cell-centered finite volume formulation using an unpwind flux differencing. Time is advanced by the Gauss-Seidel implicit scheme. Domain decomposition is accomplished by using the k-way N-partitioning method developed by Karypis. In order to analyze the parallel performance of the solver, flows over a 2-D NACA 0012 airfoil and a 3-D F-5 wing were investigated.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.2-5
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• 2011

This paper presents a numerical study on multiphase flows induced by wall adhesion The CSF(Continuum Surface Force} model is used for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing As an application of the present method, the effects of wall adhesion are numerically simulated with the CSF model for a shallow pool of water located at the bottom of a cylindrical tank. Two different cases are computed, one in which the water wets the wall and one in which the water does not wet the wall. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows induced by wall adhesion.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.31-40
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• 2011

Unsteady sheet cavitation on a three-dimensional twisted hydrofoil was studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. As a verification test of the computational method. non-cavitating and cavitating flow over a modified NACA66 foil section was simulated and validated against existing experimental data. The numerical uncertainties of forces and pressure were evaluated for three levels of mesh resolution. The computed pressure on the foil and the cavity shedding behavior were validated by comparing with existing experimental data. The cavity shedding dynamics by re-entrant jets from the end and sides of the cavity were investigated.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.572-575
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• 2008

Two-dimensional multiphase flows due to density difference such as the Rayleigh-Taylor instability problem and the droplet splash are simulated by an in-house solution code(PowerCFD). This code employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method in a volume of fluid(VOF) scheme for phase interface capturing. The present results are compared with other numerical solutions found in the literature. It is found that the present code simulates complex free surface flows such as multiphase flows due to density difference efficiently and accurately.

• 한국전산유체공학회:학술대회논문집
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• 1997.10a
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• pp.29-37
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• 1997

An implicit viscous turbulent flow solver is developed for two-dimensional geometries on unstructured triangular meshes. The flux terms are discretized based on a cell-centered finite-volume formulation with the Roe's flux-difference splitting. The solution is advanced in time using an implicit backward-Euler time-stepping scheme. At each time step, the linear system of equations is approximately solved with the Gauss-Seidel relaxation scheme. The effect of turbulence effects is approximated with a standard $k-{\varepsilon}$ two-equation model which is solved separately from the mean flow equations using the same backward-Euler time integration scheme. The triangular meshes are generated using an advancing-front/layer technique. Validations are made for flows over the NACA0012 airfoil and the Douglas 3-element airfoil. Good agreements are obtained between the numerical results and the experiment.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.98-105
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• 1999

The Pressure-based Unstructured-grid Navier-Stokes Solver PUNS-2/3D for incompressible steady and unsteady viscous flows has been developed. It is based on nonstaggered cell-centered finite volume method. Second-order upwind scheme with least-square reconstruction is used for convective fluxes. The SIMPLE method is implemented to couple the pressure and velocity fields. And the time derivatives in the momentum equations are discretised using a second-order Euler backward-differencing scheme. The discretised linear equations are solved by the preconditioned Biconjugate Gradient Stabilized method(Bi-CGSTAB). The developed solver is applied to validation problems using hybrid meshes.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.90-97
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• 1999

An implicit turbulent flow solver is developed for 2-D unstructured hybrid meshes. Spatial discretization is accomplished by a cell-centered finite volume formulation using an upwind flux differencing. Time is advanced by an implicit backward Euler time stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one equation model, which is coupled with wall function. The numerical method is applied for flows on a flat plate, the NACA 0012 airfoil, and the Douglas 3 element airfoil. The results are compared with experimental data.

• Journal of computational fluids engineering
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• v.16 no.3
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• pp.37-46
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• 2011

Unsteady sheet cavitation on a three-dimensional twisted hydrofoil was studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. As a verification test of the computational method, non-cavitating and cavitating flows over a modified NACA66 foil section were simulated and validated against existing experimental data. The numerical uncertainties of forces and pressure were evaluated for three levels of mesh resolution. The computed pressure on the foil and the cavity shedding behavior were validated by comparing with existing experimental data. The cavity shedding dynamics by re-entrant jets from the end and sides of the cavity were investigated.

• Journal of computational fluids engineering
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• v.15 no.2
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• pp.86-94
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• 2010

A thermal-hydraulic code, named CUPID, has been developed for the analysis of transient two-phase flows in nuclear reactor components. A two-fluid three-field model was used for steam-water two-phase flows. To obtain numerical solutions, the finite volume method was applied over unstructured cell-centered meshes. In steam-water two-phase flows, a phase change, i.e., evaporation or condensation, results in a great change in the flow field because of substantial density difference between liquid and vapor phases. Thus, two-phase flows are very sensitive to the local pressure distribution that determines the phase change. This in turn puts emphasis on the accurate evaluation of local pressure gradient. This paper presents a new reconstruction method to evaluate the pressure gradient at cell centers on unstructured meshes. The results of the new scheme for a simple test function, a gravity-driven cavity, and a wall boiling two-phase flow are compared with those of the previous schemes in the CUPID code.

• Journal of computational fluids engineering
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• v.6 no.1
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• pp.1-13
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• 2001

The natural convection heat transfer and solidification in a stratified pool are studied. The flow and heat transfer characteristics in a heat generating pool are compared between single-layered and double-layered pools. And local Nusselt number distributions on outer walls are obtained to consider thermal loads on a vessel wall. The cooling and solidification of Al₂O₃/Fe melt in a hemispherical vessel are simulated to study the mechanism of heat transfer and temperature distribution. A unstructured mesh is chosen for this study because of the non-orthogonality originated from the boundaries of double-layered pool. Interface between the layers is modeled to be fixed. With this assumption mass flux across the interface is neglected, but shear force and heat flux are considered by boundary conditions. The colocated cell-centered finite volume method is used with the Rhie-Chow interpolation to compute cell face velocity. To prevent non-physical solutions near walls in case body force is large the wall pressure is extrapolated by the way to include body force. The numerical solutions calculated by current method show that averaged downward heat flux of the double-layered pool increases compared to single-layered pool and maximum temperature occurs right below the interface of the layers.