• 한국전산유체공학회:학술대회논문집
• /
• 1995.10a
• /
• pp.64-69
• /
• 1995

A computer code for solving the Reynolds averaged full Navier-Stokes equations has bent developed for analysis of gas and steam turbine cascade flows with the option of using one of two types of turbulence model. One is the Baldwin-Lomax model and the other is standard $k-{\varepsilon}$ model. The numerical integration is based on the explicit four stage Runge-Kutta scheme and finite volume method. To be verified, the resulting code is applied to VKI turbine cascade and compared with the previous experimental results. Finally, the flowfield around a steam turbine cascade is analyzed. Comparisons with experimental data show that present numerical scheme is an accurate Navier-Stokes solver and can give very good predictions for both gas and steam turbine cascade flow.

• 한국전산유체공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.228-229
• /
• 2003

Complex flow field around the Darius turbine rotating stationally are simulated by solving the three dimensional incompressible Navier-Stokes equation numerically. The rotating coordinate system is employed so that the boundary conditions on the blades of the rotor become simple. In order to impose the boundary condition on the blades precisely, the boundary fitted coordinate system is employed. Fractional step method is used to solve the basic equations. The complex flow fields due to the three dimensionality of the geometry of the turbine and the rotation of the turbine are obtained and they are visualized effectively by using the technique of the computer graphics.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.115-121
• /
• 2010

Cavitating flow is widely shown in many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work focuses on the numerical analysis of the multiphase flow around the underwater vehicle which was launched from a submarine. The governing equation is the Navier-Stokes equation with a homogeneous mixture mode. The multiphase flow solver uses an implicit preconditioning scheme in curvilinear coordinate. For the code validation, the results from the present work are compared with the existing experimental and numerical results, and a reasonably good agrements are obtained. The multiphase flow around an underwater vehicle is simulated which includes submarine wake effects.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.187-194
• /
• 2010

Shape optimization of an upper plenum of PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of eight of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• Journal of computational fluids engineering
• /
• v.15 no.3
• /
• pp.1-8
• /
• 2010

Laminar separation bubble and transitional flow over the NACA0012 are investigated at a moderate range of Reynolds numbers. A Reynolds-Averaged Navier-Stokes code is coupled with an empirical transition model that can predict transition onset points and the length of transition region. Without solving the boundary layer equations, approximated e-N method is directly applied to the RANS code and iteratively solved together. The computational results are compared with the experimental data for the NACA0012 airfoil. Results of transition onset point and the length are compared well with experimental data and Xfoil prediction. The present RANS results show at high angles of attack better agreement with experimental data than Xfoil results using the boundary layer equations.

• Journal of computational fluids engineering
• /
• v.15 no.3
• /
• pp.16-23
• /
• 2010

Shape optimization of an upper plenum of a PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of height of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• 한국전산유체공학회:학술대회논문집
• /
• 1999.11a
• /
• pp.115-126
• /
• 1999

A two-dimensional Navier-Stokes solver using hybrid meshes is parallelized with a domain decompostion method. The focus of this paper is placed on minimizing the amount of effort in parallelizing the serial version of the solver, and this is achieved by adding an additional layer of cells to each decomposed domain. Most subroutines of the serial solver are used without modification, and the information exchange between neighboring domains is achieved using MPI(Message Passing Interface) library. Load balancing among the processors and scheduling of the message passing are implemented to reduce the overhead of parallelization, and the speed-up achieved by parallelization is measured on the transonic invisicd and turbulent flow problems. The parallelization efficiencies of the explicit Runge-Kutta scheme and the implicit point-SGS scheme are compared and the effects of various factors on the results are also studied.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.04a
• /
• pp.65-69
• /
• 2005

Curretly, the development of MEMS(Micro Electronic Mechanical System) technology awakes many research's interest for the aerodynamics. This work presents the development of a compact synthetic jet actuator for flow separation control at the flat plate. The formation and evolution of fluidic actuators based on synthetic jet technology are investigated using Reynolds-Averaged Navier-Stokes equations. Also, 2-Dimensional, unsteady, incompressible Navier-Stokes equation solver with single partitioning method for Multi-Block grid to analyze and a modeled boundary condition in developed fo. the synthetic jet actuator. Both laminar and turbulent jets are investigated. Results show very good agreement with experimental measurements. A jet flow develops, even though no net mass flow is introduced. Pair of counter-rotating vortices are observed near the jet exit as are observed in the experiments.

• Journal of Mechanical Science and Technology
• /
• v.15 no.3
• /
• pp.384-391
• /
• 2001

The aerodynamic effects of a 3-dimensional Wing in Ground Effect (WIG) which moves above the free surface has been numerically investigated via finite difference techniques. The air flow field around a WIG is analyzed by a Marker & Cell (MAC) based method, and the interactions between WIG and the free surface are studied by the pressure distributions on the free surface. Waves are generated by the surface pressure distribution, and a Navier-Stokes solver has been employed, to include the nonlinearities in the free surface conditions. The pressure values Cp and lift/drag ratio are reviewed by changing the height/chord ratio. In the present computations a NACA0012 airfoil with a span/chord ratio of 3.0 are treated. Through computational results, it is confirmed that the free surface can be treated as a rigid wavy wall.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.4
• /
• pp.541-550
• /
• 1997

Computational and experimental investigations on the three-dimensional flowfield through an automotive cooling fan are carried out in this work. Steady, incompressible, three-dimensional, turbulent flow through a rotating axial-flow fan is analyzed with Reynolds averaged Navier-Stokes equations and standard k-.epsilon. turbulence model. The governing equations are discretized with finite-volume approximations in non-orthogonal curvilinear coordinates. Computational static pressures on the casing wall agree well with the experimental data which are measured in this work. And, they are sensitive to the change of tip clearance. The flowfield is not significantly affected by the thickness of the blade. The k-.omega. model gives the static pressure rise on the casing wall which is similar to that with the k-.epsilon. model.