• 대한기계학회논문집
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• 제19권10호
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• pp.2617-2629
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• 1995

The flow through a centrifugal compressor rotor was calculated using the quasi-3-dimensional and fully 3-dimensional Navier-Stokes solution methods. The calculated results, obtained during the development of the computer codes for both methods are discussed. In the inviscid quasi 3-dimensional analysis, stream function formulation was used for the blade to blade (B-B) plane calculations, and the streamline curvature method was used for the meridional (H-S) plane calculations. In the viscous 3-dimensional flow analysis, a control volume method based on a general rotating curvilinear coordinate system was used to solve the time-averaged Navier-Stokes equations, and a standard k-.epsilon. model was used to obtain eddy viscosity. The quasi-3-dimensional analysis reasonably predicts the pressure distributions and requires much less computation time in the region where viscous effects are not strong; however, it fails to predict velocity field and loss mechanism through the impeller passage. The viscous 3-dimensional flow analysis shows reasonable pressure distributions and typical jet-wake flow field through the impeller passage. Secondary flow and total pressure distributions on cross-sectional planes explain the loss mechanisms through the impeller.

• 대한기계학회논문집
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• 제16권10호
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• pp.1915-1927
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• 1992

본 연구에서는 3차원 압축성 내부유동해석 코드를 개발하여 터어빈 정익이나 동익 내부의 차원 익렬 유동을 수치적으로 해석하고자 한다. 여기에서 사용된 코드 는 Obyashi의 LU-ADI기법을 이용한 기존의 2차원 익렬 유동해석 코드를 3차원 유동장 으로 학장한 것이고, 난류유동해석에는, Baldwin-Lomax의 박층 대수모델을 3차원으로 확장한 알고리즘을 적용하였다.Kiock등이 실험한 선형 터어빈 익렬 내부의 천음속 유동장에 적용하여 양끝 벽면에 의한 3차원 유동장 특성을 분석하고, 3차원 익렬 유동 코드의 적합성을 검토하였다.

• 대한기계학회논문집
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• 제18권12호
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• pp.3287-3296
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• 1994

For the numerical computation of three-dimensional compressible flow field within a blade row in a centrifugal compressor, a quasi 3-dimensional solver which combines a reversible B-B flow and an irreversible H-S flow using finite element methods was developed. In a reversible B-B flow, the governing coordinates are modified in order to be applied to any type of turbomachinery, and two kinds of stream functions are introduced in order to make the Kutta condition exactly satisfied. In an irreversible H-S flow, the changes of entropy in the irreversible governing equations are determined not by empirical source but by the theoretical treatment of dissipation forces. The dissipation forces are obtained from the distribution of shear stresses in the flow passage which are given from the wall shear stresses using the exponential functions. A more accurate quasi-3-dimensional solver is established where the effect of body forces is involved in the non-axisymmetric H-S flow. Some numerical results obtained from authors' previous studies for axial flow machines assure that the present method is able to predict well as long as the flow is subsonic and not under strong viscous effect.

• 대한기계학회논문집
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• 제13권5호
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• pp.1044-1051
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• 1989

본 연구에서는 Wu가 제시한 수학적 모델에 기초를 둔 비점성 준3차원 유동해 석에 실제 유체의 점성효과 및 2차유동 등에 의해 발생하는 손실들을 손실모델로 반영하여 그 타당성 유무를 검토하는 데 목적을 두었다.

• 한국전산유체공학회지
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• 제5권3호
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• pp.23-31
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• 2000

The three-dimensional unsteady compressible Full Navier-Stokes equation solver with sliding multi-block method has been applied to analyze three dimensional characteristics of the viscous flow field and compression wave around the high speed train which is entering into a tunnel. The numerical scheme of AF + ADI was used to efficiently solve Navier-Stokes equations in the curvilinear coordinate system. The vortex formation owing to the viscous interaction around the train was found and the generation of compression wave due to the blockage effects was observed ahead of the train in the form of plane wave. The three dimensional characteristics of the flow field compared to the analytic results were discussed in detail. The variation of pressure of tunnel wall surface and velocity profile of the train are identified as the train enters into a tunnel. The changes in aerodynamic forces and streamlines of each specific sections are also discussed.

• 동력기계공학회지
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• 제18권3호
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• pp.79-86
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• 2014

Mixed convective vortex flow in the three-dimensional rectangular channel filled with high viscous fluid(Pr=909) is investigated computationally under various operating conditions. The Reynolds number is varied from 0 to $5{\times}10^{-1}$, the Rayleigh number from $10^3$ to $5{\times}10^4$. The three-dimensional governing equations are discretized using the finite volume method. The effects of Reynolds number and Rayleigh number are presented and discussed. From a parametric study, it is found that vortex flow pattern of mixed convection in rectangular channels can be classified into three flow patterns basically, but the new vortex flow structures containing wave rolls are found, which are affected by Rayleigh number and Reynolds number. From this results, we can draw a flow regime map to delineate various vortex flow patterns in the high viscosity fluid mixed convective flow.

• Journal of applied mathematics & informatics
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• 제7권3호
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• pp.801-812
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• 2000

Two-dimensional slow viscous flow on infinite half-plane past a perpendicular infinite cavity is considered on the basis of the Stokes approximation. Using complex representation of the two-dimensional Stokes flow, the problem is reduced to solving a set of Fredholm integral equations of the second kind. The streamlines and the pressure and vorticity distribution on the wall are numerically determined.

• 연구논문집
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• 통권24호
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• pp.107-117
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• 1994

In aerodynamic design of centrifugal compressors, impellers are designed through preliminary design and blade profile generation. In order to find out faults of the initially designed impellers, the detailed informations about internal flow phenomena such as pressure distribution, flow separation, blade loading, etc are essential. These informations can be acquired with flow measurements or computational flow analyses. In this study, we calculated 3-D viscous flow in 4 back-swept impellers which were designed in our laboratory, and analyzed the flow characteristics which influence the performance of impellers.

• Journal of Mechanical Science and Technology
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• 제19권3호
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• pp.877-886
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• 2005

Two-dimensional incompressible Navier-Stokes equations are solved using SIMPLER method in the intrinsic curvilinear coordinates system to study the unsteady viscous flow physics over two-dimensional ellipses. Unsteady viscous flows over various thickness-to-chord ratios of 0.6, 0.8, 1.0, and 1.2 elliptic cylinders are simulated at different Reynolds numbers of 200, 400, and 1,000. This study is focused on the understanding the effects of Reynolds number and elliptic cylinder thickness on the drag and lift forces. The present numerical solutions are compared with available experimental and numerical results and show a good agreement. Through this study, it is observed that the Reynolds number and the cylinder thickness affect significantly the frequencies of the force oscillations as well as the mean values and the amplitudes of the drag and lift forces.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.777-782
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• 2000

The flow fields in the volute casing of a small-size turbo-compressor at different flowrate (design point ${\pm}20%$) are studied by numerical analysis. The governing equations for three-dimensional steady viscous flow are solved using SIMPLE algorithm with commercial code of STAR-CD. Numerical results show that the three-dimensional flow pattern inside the volute casing of a small-size turbo-compressor is strongly influenced by secondary flows that are typically created by the curvature or the casing passages. The flow pattern in the casing also affects the performance of the turbo-compressor. In order to elucidate the loss mechanism through the volute, we prepared the secondary flow, velocity magnitude, and static pressure distribution at the four cross-sectional planes of the casing.