• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 추계 학술대회논문집
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• pp.3-10
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• 1995

The compressible laminar and turbulent viscous flow on a slender body in supersonic speed as well as subsonic speed has been numerically simulated at high angle of attack. The steady and time-accurate compressible thin-layer Navier-Stokes code based on an implicit upwind-biased LU-SGS algorithm has been developed and specifically applied at angles of attack of 20, 30, 40 deg, respectively. The modified eddy-viscosity turbulence model suggested by Degani and Schiff was used to simulate the case of turbulent flow. Any geometric asymmetry and numerical perturbation have not been intentionally or artificially imposed in the process of computation. The purely numerical results for laminar and turbulent cases, however, show clear asymmetric formation of vortices which were observed experimentally. Contrary to the subsonic results, the supersonic case shows the symmetric formation of vortices as indicated by the earlier experiments.

• 한국유체기계학회 논문집
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• 제2권1호
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• pp.43-49
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• 1999

Flow field and near-field noise of a centrifugal fan has been studied with an efficient compressible method and STAR-CD. The flow field of the centrifugal fan is assumed to be two-dimensional. Most of the compressible studies have been done by inviscid solver because viscous simulation shows little difference. The near field noise is estimated in terms of sound pressure level in frequency domain transformed from the computed pressure fluctuations using FFT. The simulation has been done on various design elements such as impeller blade shapes, the number of blades and cut-off clearance. The comparison shows that the number of blades has a significant effect on near-field noise without losing aerodynamic performance.

• 대한기계학회논문집
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• 제12권6호
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• pp.1407-1414
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• 1988

본 연구에서는 저자들에 의해 이미 개발된 경계유선수정법에 의한 B-B 유동계 산을 통해 익열의 편차각을 계산하고 기존의 예측방법에 의한 결과와 비교 검토하여 압축성 및 3차원 비축대칭성의 효과를 검토하였다.

• Coupled systems mechanics
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• 제6권4호
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• pp.439-464
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• 2017

The hydro-elastic system consisting of a pre-stretched highly elastic plate, compressible Newtonian viscous fluid, and the rigid wall is considered and it is assumed that on the plate a lineal-located time-harmonic force acts. It is required to investigate the dynamic behavior of this system and determine how the problem parameters and especially the pre-straining of the plate acts on this behavior. The elasticity relations of the plate are described through the harmonic potential and linearized (with respect to perturbations caused by external time-harmonic force) form of these relations is used in the present investigation. The plane-strain state in the plate is considered and the motion of that is described within the scope of the three-dimensional linearized equations of elastic waves in elastic bodies with initial stresses. The motion of the fluid is described by the linearized Navier-Stokes equations and it is considered the plane-parallel flow of this fluid. The Fourier transform with respect to the space coordinate is applied for a solution to the corresponding boundary-value problem. Numerical results on the frequency response of the interface normal stress and normal velocity and the influence of the initial stretching of the plate on this response are presented and discussed. In particular, it is established that the initial stretching of the plate can decrease significantly the absolute values of the aforementioned quantities.

• 한국전산유체공학회지
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• 제1권1호
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• pp.112-122
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• 1996

A finite element scheme using the concept of PISO method has been developed to solve the Navier-Stokes viscous flows in all speed range. This scheme includes development of new pressure equation that retains both the hyperbolic term related with the density variation and the elliptic term reflecting the incompressibility constraint. The present method is applied to the incompressible two-dimensional driven cavity flow problems(Re=100, 400 and 1,000). For compressible flows, the Carter plate problem(M=3 and Re=1,000) is computed. Finally, we have simulated the shock-boundary layer interaction(M=2 and Re=2.96×10/sup 5/), a more difficult problem, and compared its results with the experiment to demonstrate the shock capturing capability of the present solution algorithm.

• 대한기계학회논문집B
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• 제22권2호
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• pp.240-252
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• 1998

The purpose of this study is to develop a method for predicting the aerodynamic performance of the low speed airfoils in the 2-dimensional, steady and viscous flow. For this study, the airfoil geometry is specified by adopting the longest chord line system and by considering local surface curvature. In case of the inviscid incompressible flow, the analysis is accomplished by the linearly varying strength vortex panel method and the Karman-Tsien correction law is applied for the inviscid compressible flow analysis. The Goradia integral method is adopted for the boundary layer analysis of the laminar and turbulent flows. Viscous and inviscid solutions are converged by the Lockheed iterative calculating method using the equivalent airfoil geometry. The analysis of the separated flow is performed using the Dvorak and Maskew's method as the basic method. The wake effect is also considered by expressing its geometry using the formula of Summey and Smith when no separation occurs. The computational efficiency is verified by comparing the computational results with experimental data and by the shorter execution time.

• 대한기계학회논문집
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• 제15권1호
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• pp.229-240
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• 1991

본 연구에서 사용한 이론과 제시된 방법의 타당성을 검토하기 위하여 익열 간 극이 무한대인 단일 익형 주위의 유동장을, 최근에 개발된 계산방법인 Lambda방법을 사용한 Dadone의 해석결과와 비교하였고, 범용의 압축기 익형인 NACA65게열 익열 유동 에 대한 Herrig의 실험값, 그리고 미분해석에 의한 점성-비점성 상호작용 방법을 사용 한 Hansen의 계산값고, 이들 조건과 동일한 상태에서 본 연구에서 제시한 방법으로 계 산한 결과와 만족할 만한 일치를 얻었다.

• 한국항공우주학회지
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• 제35권8호
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• pp.677-684
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• 2007

본 연구에서는 삼차원 점성 유동을 효율적으로 해석하기 위해 사면체, 프리즘, 피라미드를 포함하는 비정렬 혼합격자계를 기반으로 하는 유동해석코드를 개발하였다. 유동의 지배방정식은 격자점 중심의 유한체적법을 사용하여 공간차분회었으며, 제어테적은 메디안 듀얼(median-dual)방법으로 구성하였다. 난류유동 해석은 Spalart-Allmaras 난류모형과 연계하여 계산되었다. 개발된 해석코드의 정상 유동 검증을 위해 삼차원 날개에 대한 층류, 난류유동을 해석하였으며, 비정상 유동 검증을 위해 조화운동에 의해 진동하는 삼차원 날개에 대한 유동해석을 수행하였다.

• 대한기계학회논문집
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• 제12권1호
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• pp.106-115
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• 1988

본 연구에서는 경계층 유동을 충류, 천이, 난류 영역을 포함하는 압축성 유동으로 가정하였고, Morgan 등이 제시한 새로운 질점분할 방법을 사용하여 속도분포를 계산하고, 점성 압축성 효과를 고려하기 위하여 viscous--inviscid interaction 법을 사용하였고 이 계산 결과를 기존의 실험값과 비교하여,타당성을 확인하였다.그리고 최적 양력의 익형 설계는 Augmented Lagrange multiplier 법을 사용하였고 비구속 조건을 갖는 목적함수 augmented lagrangian의 최소화는 Davidan-Fletcher-Powell 방법 중 self-scaling quasi-Newton algorithm을 사용하였다. 그리고 NACA 23012를 기본 익형으로 하고 NACA 64-2-415, NACA 64-2-A215, NACA 65-3-218를 보상 익형으로 하여 최대 양력익형을 설계 하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2002년도 춘계 학술대회논문집
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• pp.59-64
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• 2002

In this paper, the preconditioned multistage time stepping methods which are popular multigrid smoothers is implemented for the compressible Navier-Stokes calculation with full-coarsening multigrid method. The convergence characteristic of the point-Jacobi and Alternating direction line Jacobi(DDADI) preconditioners are studied. The performance of 2nd order upwind numerical fluxes such as 2nd order upwind TVD scheme and MUSCL-type linear reconstruction scheme are compared in the inviscid and viscous turbulent flow caculations.