• 한국해양공학회지
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• 제12권2호통권28호
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• pp.79-86
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• 1998

A three-dimensional WIG (Wing In Ground effect) moving above free surface is numerically studied by means of finite difference techniques. The air flow field around the WIG is analyzed by MAC (Marker & Cell) method, and interactions between WIG and the free surface are appeared as the variation of pressure distribution acting on the free surface. To analyze the wavemaking phenomena by those pressure distributions, the NS (Navier-Stokes) solver is employed in which nonlinearities of the free surface conditions can be included. Through the numerical simulation, Cp values and lift/drag ratio are carefully reviewed by changing the height/chord ratio. The section shape of model is NACA0012 with the span/chord ratio of 3.0. Through computational results, it is confirmed that the effect of free surface is small enough to treat it as a rigid wavy wall.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 추계 학술대회논문집
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• pp.64-69
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• 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
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.115-121
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• 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
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• 한국전산유체공학회 2005년도 춘계 학술대회논문집
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• pp.65-69
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• 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
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• 제15권3호
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• pp.384-391
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• 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.

• 대한기계학회논문집B
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• 제32권4호
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• pp.317-326
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• 2008

The main purpose of the present study is to perform shape optimizations of transonic compressor blade in order to enhance its performance. In this study, the Latin hypercube sampling of design of experiments and the weighted average surrogate model with the help of a gradient based optimization algorithm are used within design space by the lower and upper limits of each design variable and for finding optimum designs, respectively. 3-D Reynolds-averaged Navier-Stokes solver is used to evaluate the objective functions of adiabatic efficiency and pressure ratio. Six variables from lean and airfoil thickness profile are selected as design variables. The results show that the adiabatic efficiency is enhanced by 1.43% by efficiency optimization while the pressure ratio is increased very small, and pressure ratio is increased by 0.24% by pressure ratio optimization.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.106-112
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• 1999

In this article, combination of the FAS-FMG multi-grid method and the Krylov subspace method was presented in solving two dimensional driven-cavity flows. Three algorithms of the Krylov subspace method, CG, CGSTAB(Bi-CG Stabilized) and GMRES method were tested with MILU preconditioner. As a smoother of the pressure correction equation, the MILU-CG is recommended rather than MILU-GMRES(k) or MILU-CGSTAB, since the MILU-GMRES(k) preconditioner has too much computation on the coarse grid compared to the MILU-CG one. As for the momentum equation, relatively cheap smoother like SIP solver may be sufficient.

• 한국전산유체공학회지
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• 제14권4호
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• pp.78-85
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• 2009

Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work has focused on the simulation of cavitating flow past cylinders with strong side flows. The governing equation is the Navier-Stokes equation based on the homogeneous mixture model. The momentum and energy equation is in the mixture phase while the continuity equation is solved liquid and vapor phase, separately. An implicit dual time and preconditioning method are employed for computational analysis. For the code validation, the results from the present solver have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained. After the code validation, the strong side flow was applied to include the wake flow effects of the submarine or ocean tide.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권3호
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• pp.256-266
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• 2012

Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, torpedoes, etc. The present work has developed the base code to solve the cavitating flows past the axisymmetric bodies with several forebody shapes. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. The momentum is in the mixture phase while the continuity equation is solved in liquid and vapor phase, separately. The solver employs an implicit preconditioning algorithm in curvilinear coordinates. The computations have been carried out for the cylinders with hemispherical, 1-caliber, and 0-caliber forebody and, then, compared with experiments and other numerical results. Fairly good agreements with experiments and numerical results have been achieved. It has been concluded that the present numerical code has successfully accounted for the cavitating flows past axisymmetric bodies. The present code has also shown the capability to simulate ventilated cavitation.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.200-207
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• 1999

An efficient inverse design technique based on the MGM (Modified Garabedian-McFadden) method has been developed. The 2-D Navier-Stokes equations are solved for obtaining the surface pressure distributions and coupled with the MGM method to perform the inverse design. The solver is parallelized by using the domain decomposition method and the standard MPI library for communications between the processors. The MGM method is a residual-correction technique, in which the residuals are the difference between the desired and the computed pressure distribution. The developed code was applied to several airfoil shapes and the axial blade. It has been found that they are well converged to their target pressure distribution.