• 한국전산유체공학회지
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• 제4권1호
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• pp.41-52
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• 1999

이 논문에서는, QUICK해법의 불안정성을 개량하므로써, 수치계산에 있어서 수렴이 빠르고, 수치적으로 안정한 계산을 할 수 있는 새로운 MQUICK 상류해법을 제안하고, 이를 비압축성 층류유동의 계산에 적용하였다. 또한, 해법의 정확성, 안정성, 수렴속도에 대한 검토를 통하여 본 MQUICK 상류해법의 유효성과 타당성이 평가되었다. 이 해법에서는 인공산일의 가감을 조절하기 위하여 가중계수 α를 써서 정식화 하였고, 위의 검토를 통하여 α의 최적값을 조사하였다. 이 해법을 SMAC 음해법에 적용하여 2 차원 공동유동, 3 차원 덕트유동과 같은 몇몇 표준문제를 계산하고, 계산된 결과를 실험값 또는, 3 차 정확도의 상류해법 및 QUICK해법에 의한 결과 들과 비교 하므로써, 본 MQUICK 상류해법이 위의 다른 해법에 비하여 안정하고, 유효성이 높은 해법임을 확인 하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.597-602
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• 2000

In a MEMS(micro-electro mechanical system), the fluid may slip near the surface of a solid and have a discontinuous temperature profile. A numerical prediction in this slip flow region can provide a reasonable guide for the design and fabrication of micro devices. The compressible Navier-Stokes equation with Maxwell/smoluchowski boundary condition is solved for two simple systems; couette flow and pressure driven flow in a long channel. We found that the couette flow could be regarded as an incompressible system in low speed regions. For the pressure driven flow system, we observed nonlinear distribution of pressure in the long channel and numerical results showed a good agreement with the experimental results.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.177-185
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• 1999

The airfoil design optimization procedures based on the Navier-Stokes equations were developed, This procedure enables more realistic and practical transonic airfoil designs. The modified Hicks-Henne functions were used to generate the shape of airfoils. Five Hick-Henne functions were used to design upper surface of airfoil only. To enhance the ability of Hick-Henne function to generate various airfoil shape with limited number of functions, the positions of control points were adjusted through optimization procedure. The design procedure was applied to the single-point design for the drag minimization problem with lift and area constraints. The result shows the capability of the procedure to generate much realistic airfoils with very small drag-creep in the low transonic regime. This is mainly due to the viscosity effect of Navier-Stokes flow analysis. However, in the higher transonic range tile drag-creep appears. The multi-point design is shown to be an effective way to avoid the drag-creep and improve off-design performance which is very similar in the Euler design.

• 대한설비공학회지:설비저널
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• 제13권1호
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• pp.5-13
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• 1984

This analysis of numerical procedure is prediction of laminar flow and heat transfer at two dimension and steady flow in asymmetric sudden expansion channel. At former study, to analyse the flows with separation, the full Navier-Stokes equation is used, but there are many difficulties to analyse, and although significant progress has been made in the development of efficient computational methods for the Navier-Stokes equations, very large computation times are still required. In case of reward-facing flow, boundary-layer equation is used instead of full Navier-Stokes equation to analyse velocity fields, and result of this numerical analysis is good agreement with the given experimental study. In this case, since the computer time required for the boundary-layer calculation is an order of magnitude less than required for the solution of the full Navier-Stokes equation, this boundary-layer model provides a good approximate solution.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1335-1342
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• 2000

Three-dimensional flow analysis and numerical optimization methods are presented for the design of an axial-flow fan. Steady, incompressible, three-dimensional Reynolds-averaged Navier-Stokes equations are used as governing equations, and standard k- ${\varepsilon}$ turbulence model is chosen as a turbulence model. Governing equations are discretized using finite volume method. Steepest descent method, conjugate gradient method and BFGS method are compared to determine the searching directions. Golden section method and quadratic fit-sectioning method are tested for one dimensional search. Objective function is defined as a ratio of generation rate of the turbulent kinetic energy to pressure head. Two variables concerning sweep angle distribution are selected as the design variables. Performance of the final fan designed by the optimization was tested experimentally.

• 대한기계학회논문집B
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• 제24권7호
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• pp.907-915
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• 2000

The preconditioned Krylov subspace methods were applied to the incompressible Navier-Stoke's equations for convergence acceleration. Three of the Krylov subspace methods combined with the five of the preconditioners were tested to solve the lid-driven cavity flow problem. The MILU preconditioned CG method showed very fast and stable convergency. The combination of GMRES/MILU-CG solver for momentum and pressure correction equations was found less dependency on the number of the grid points among them. A guide line for stopping inner iterations for each equation is offered.

• 한국수자원학회논문집
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• 제43권9호
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• pp.801-811
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• 2010

급경사에서의 고립파의 처오름을 예측하기 위해 3차원 수치모형에 내부조파기법을 도입하여 수치모형실험을 수행하였다. 수치모형은 Navier-Stokes 방정식을 유한차분법을 이용하여 계산하는 동수압 모형으로서, 난류의 해석을 위해서 상대적으로 큰 에디(eddy)만을 고려하는 SANS(spatially averaged Navier-Stokes) 방정식을 푸는 LES(large-eddy-simulation) 기반의 수치모형을 사용한다. 엇갈림 격자체계에서 유한차분법을 사용하여 지배방정식을 해석하는 모형으로서 수치기법으로 Two-step projection 기법을 사용하여 SANS 방정식을 풀었으며, Poisson 방정식을Bi-CGSTAB 기법을 이용하여 풀고 압력장을 계산하였다. 또한, 자유수면의 추적을 위하여 2차 정확도의 VOF(volume-of-fluid) 기법을 사용하였다. 먼저 고립파를 3차원 공간의 일정 수심상에서 내부조파하여 해석해와 비교한 후 분산오차에 대해 분석하였다. 그리고 고립파를 내부조파하여 급경사에서의 고립파의 처오름 및 처내림 현상을 예측하고 수리모형 실험결과와 비교 및 분석하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.221-226
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• 1999

Three-dimensional flow analysis and numerical optimization methods are presented for the design of an axial-flow fan. Steady, Incompressible, three-dimensional Reynolds-averaged Wavier-Stokes equations are used as governing equations, and standard k-$\epsilon$ turbulence model is chosen as a turbulence model. Governing equations are discretized using finite volume method. Steepest descent method, conjugate gradient method and BFGS method are compared to determine the searching directions. Golden section method and quadratic fit-sectioning method are tested for one dimensional search. Objective function is defined as a ratio of generation rate of the turbulent kinetic energy to pressure head. Sweep angle distributions are used as design variables.

• 한국전산구조공학회논문집
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• 제15권4호
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• pp.661-674
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• 2002

본 연구의 목적은 Navier-Stokes 유체의 최적 제어 문제의 해를 얻을 수 있는 효과적인 수치해석기법을 개발하고, 이를 물체의 항력(drag)을 최소화하는 문제에 적용하는데 있다. 본 연구는 항력을 줄인다는 산업적인 중요성과 함께 최적 제어를 위한 하나의 효과적인 최적화 기법의 모델을 제공하고 있다. 항력을 줄이기 위한 방법으로써 물체의 경계면에서 유체의 흡입(suction)과 방출(injection)이라는 기법을 사용하여 경계면에서 속도를 제어하였고, 목적함수로써 항력을 표현하기 위하여 에너지 소실의 변화율을 사용하였다. 컴퓨터 용량을 최소화하고 최적화에서의 해의 보장성과 경제성을 위하여, Navier-Stokes의 해석을 위하여 페널티 방법을 사용하였고 최적화 기법을 위해서는 SQP 방법을 사용하였다. 그리고 Navier-Stokes 유체는 대단히 비선형성을 나타내기 때문에 최적화를 수행하기에는 매우 힘들다. 이를 위하여 연속기법(continuation technique)을 사용하였다.

• 대한수학회지
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• 제36권1호
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• pp.159-171
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• 1999

We formulate and study a finite element method for a linearized steady state, compressible, viscous Navier-Stokes equations in 2D, based on the discontinuous Galerkin method. Dislike the standard discontinuous galerkin method, we do not assume that the triangle sides be bounded away from the characteristic direction. the unique stability follows from the inf-sup condition established on the finite dimensional spaces for the (incompressible) Stokes problem. An error analysis having a jump discontinuity for pressure is shown.