• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.140-146
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• 2002

The fluid induced vibration (FIV) phenomena of a 2-D.O.F airfoil system have been investigated in low Reynolds number incompressible flow region. Unsteady flows with viscosity are computed using two-dimensional incompressible Navier-stokes code. To validate developed Navier-Stokes code, steady and unsteady flow fields around airfoil are analyzed. The present fluid/structure interaction analysis is based on the most accurate computational approach with computational fluid dynamics (CSD) and computational structural dynamics (CSD) techniques. The highly nonlinear fluid/structure interaction phenomena due to severe flow separations have been analyzed fur the low Reynolds region (R$_{N}$ =500~5000) that has a dominancy of flow viscosity. The effect of R$_{N}$ on the fluid/structure coupled vibration instability of 2-DOF airfoil system is presented and the effect of initial angle of attack on the dynamic instability are also shown.own.

• 한국추진공학회지
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• 제6권1호
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• pp.71-82
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• 2002

본 연구에서는 2차원의 압축성 Navier-Stokes 코드를 개발하여 mixer-ejector 노즐의 유동장 해석을 다양한 덕트와 노즐 면적비 및 노즐 압력비에 대하여 계산을 수행하였다. 덕트와 노즐 면적비 계산에서는 먼저 효율적인 2차 유동의 유입을 위한 최적의 면적비가 있음을 볼 수 있었다. 높은 면적비에서는 입구 자유유동의 적절한 혼합없이 mixing duct를 그대로 통과하는 것을 볼 수 있었고, 낮은 면적비에서는 제트의 경계가 유입 유동에 장애물로 작용하는 것을 볼 수 있었다. 노즐 압력비의 계산에 있어서는 shroud 벽면과 shock cell structure 간에 상호작용이 작다면 유입유량은 압력비에 따라 증가하는 것을 볼 수 있었다.

• 대한조선학회논문집
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• 제48권6호
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• pp.581-591
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• 2011

This paper describes the air compressibility effect in the CFD simulation of water impact load prediction. In order to consider the air compressibility effect, two sets of governing equations are employed, namely the incompressible Navier-stokes equations and compressible Navier-Stokes equations that describe general compressible gas flow. In order to describe violent motion of free surface, volume-of-fluid method is utilized. The role of air compressibility is presented by the comparative study of water impact load obtained from two different air models, i.e. the compressible and incompressible air. For both cases, water is considered as incompressible media. Compressible air model shows oscillatory behavior of pressure on the solid surface that may attribute to the air-cushion effect. Incompressible air model showed no such oscillatory behavior in the pressure history. This study also showed that the CFD simulation can capture the formation of air pockets enclosed by water and solid surface, which may be the location where the air compressibility effect is dominant.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1636-1640
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• 2006

SMAC method, one of the computational fluid dynamics techniques, is modified from the original MAC method for the time-dependent variation of flow analysis. The Navier-Stokes equations for incompressible time-dependent viscous flow are applied, and also marker particles that present the visualization of flow analysis are used. In this study SMAC technique is used to analyze the flow behavior in the water-filling of virtual channel. Then by changes of diameter of two ingates, the change of velocity and discharge when two ingates are filled the water to virtual channel are simulated. As a result, water-filling flow pattern in the virtual channel is simulated very well. Therefore, this numerical simulation will also be applied for the design of structures as open flume and porous breakwater.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.75-80
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• 2005

The present work was undertaken to numerically analyze the defrosting phenomena of windshield glass. In order to analysis the phase change from frost to water on windshield glass by discharging hot air from a defroster nozzle, the flow and the temperature field of the cabin interior, the heat transfer through the windshield glass, and the phase change of frost should be solve simultaneously. In the present work, the flow field was obtained by solving 3-D incompressible Navier-Stokes equations, and the temperature field was computed from the incompressible energy equation. The phase change process was solved by the enthalpy method. For the code validation, the temperature and the phase change of the driven cavity were calculated. The calculation showed a good agreement with other numerical results. Then, the present code was applied to the defrosting problem of a real automobile, and a good agreement with the experimental data was also obtained.

• 한국자동차공학회논문집
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• 제11권2호
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• pp.157-163
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• 2003

This work was undertaken for the numerical analysis of defrosting phenomena of automobile windshield. To analyze the defrost, the flow and temperature field of cabin interior, heat transfer through the windshield glass, and phase change of the frost should be analyzed simultaneously. The flow field was obtained by solving the 3-D unsteady Navier-Stokes equation and the temperature field was computed by energy equation. The phase-change process of Stefan problem was solved by enthalpy method. For code validation, the temperature field of the driven cavity was calculated. The result of calculation shows a good agreement with the other numerical results. Then, the present code was applied to the defrosting analysis of a real automobile and, also, a good agreement with experiment was obtained.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.235-242
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• 2003

This paper deals with numerical analysis of static and dynamic wind effects on civil engineering structures. Aeroelastic analysis becomes a prime criterion to be confirmed during the structural design because the long-span suspension bridges are prone to the aerodynamic instabilities caused by wind. If the wind velocity exceeds the critical velocity that the bridge can withstand, then the bridge fails due to the phenomenon of flutter. The aeroelastic simulation is carried out using both Computational Fluid Dynamic(CFD) and Computational Structural Dynamic(SCD) schemes.

• 한국전산구조공학회논문집
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• 제20권5호
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• pp.661-669
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• 2007

바람에 저항하는 초고층 건물, 비행기나 자동차, 물에 저항하는 선박 등은 동일한 거동을 보여준다. 즉, 유속이 빨라 질경우, 건물 혹은 비행기, 자동차, 선박 뒤편에는 마이너스 압력과 와류가 발생하게 되는데 이로 인해 건물에서는 변위가 크게 발생하게 되고, 비행기나 자동차, 선박 등에서는 속력이 저하된다. 본 연구에서는 흡입과 방출이라는 기법을 이용하여 유체의 흐름을 우리가 원하는대로 적극적으로 제어하고자 한다. 그렇게 할 수만 있다면 초고층 건물에서의 변위를 대폭 줄일 수 있을 것이고, 자동차나 비행기 선박 등은 더 빠른 속도로 달릴 수 있을 것이다. 그렇다면 문제는 유체를 제어하기 위한 최적의 흡입 혹은 방출량을 구하는 것이고, 이 최적의 양들을 어떤 방법으로 구하는 것이냐 하는 것이다. 본 연구는 최적화 기법을 사용하여 Navier-Stokes 유체를 받는 물체의 표면에서 최적의 흡입, 그리고 방출량을 결정하려는 시도에서 출발하였다. 그러나 이 문제는 큰 Reynols Number 상태에서는 높은 비선형성으로 인하여 직접 한번에 Navier-Stokes 유체의 해석조차 불가능하였고, 더군다나 너무나 많은 변수로 인하여 기존의 방법으로는 최적화는 도저히 불가능 하였다. 본 연구에서는 이를 해결하기 위한 최적화 알고리즘을 제안하고, 또한 수렴속도도 대폭 증가시키기 위한 매우 효율적인 몇 가지 방법들을 제안하였다.

• 한국유체기계학회 논문집
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• 제15권4호
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• pp.19-26
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• 2012

In this paper, a parametric study on ribs which are installed in an equilateral triangular internal cooling channel is presented. The numerical analysis of the flow structure and heat transfer characteristics is performed using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. The numerical results are obtained at Reynolds number, 20,000. The parametric study is performed for the parameters, the angle of a rib, rib pitch-to-hydraulic diameter ratio, rib width-to-hydraulic diameter ratio, and rib height-to-hydraulic diameter ratio. The computational results are validated with the experimental data for area-averaged Nusselt number.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.684-689
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• 2001

In this study, three-dimensional viscous flow analysis and optimization are presented for the design of a mixed-flow fan. Steady, imcompressible, three-dimensional Reynolds averaged Navier-Stokes equations are used as governing equations, and standard $k-{\varepsilon}$ turbulence model is chosen as a turbulence model. Governimg equations are discretized using finite volume method. Upwind difference scheme is used for the discretization of the convective term and SIMPLEC algorithm is used as a velocity-pressure correction procedure. The computational results are compared with the results obtained by TASCflow. For the numerical optimization of the design, objective function is defined as a ratio of generation of the turbulent energy to pressure head. Sweep angles are used as design variables.