• Title/Summary/Keyword: Three-Dimensional Reynolds-Averaged Navier-Stokes Equation

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ANALYSIS OF HEAT TRANSFER OF INCLINED IMPINGING JETS ON A CONCAVE SURFACE (엇갈리게 기울어진 충돌제트들에 의한 오목면 상의 열전달 성능해석)

  • Heo, M.W.;Lee, K.D.;Kim, K.Y.
    • Journal of computational fluids engineering
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    • v.16 no.2
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    • pp.11-16
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    • 2011
  • Numerical analyses have been carried out to analyze the three-dimensional turbulent heat transfer by impingement jet on a concave surface with variation of geometric configurations. Three-dimensional Reynolds averaged Navier-stokes equations have been calculated using the shear stress transport turbulent model. The numerical results for heat transfer rate were validated in comparison with the experimental data. The distance between jet nozzles and angle of inclined jet nozzle were selected as the geometric variables. Area-averaged Nusselt numbers on concave surface are evaluated to find the characteristics of heat transfer with the two geometric variables. The heat transfer increases as the distance between jet nozzles increases, and the inclined impinging jets show much better heat transfer performance than the vertical impinging jet.

Three-Dimensional Navier-Stokes Analysis of the Flow through A Multiblade Centrifugal Fan (원심다익송풍기 유동의 삼차원 Navier-Stakes 해석)

  • Seo, Seoung-Jin;Chen, Xi;Kim, Kwang-Yong;Kang, Shin-Hyung
    • 유체기계공업학회:학술대회논문집
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    • 1998.12a
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    • pp.42-48
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    • 1998
  • Numerical study is presented for the analysis of three-dimensional incompressible turbulent flows in multiblade centrifugal fan. Reynolds-averaged Navier-Stokes equations with standard k - $\epsilon$ turbulence model are transformed to non-orthogonal curvilinear coordinates, and are discretized with finite volume approximations. Linear Upwind Differencing Scheme(LUDS) is used to approximate the convection terms in the governing equations. SIMPLEC algorithm is used as a velocity-pressure correction procedure. The computational area is divided into three blocks; core, impeller and scroll, which are linked by multi-block method. The flow inside of the fan is regarded as steady flow, and mathematical formula established from the cascade theory and empirical coefficient are employed to simulate tile flow through the impeller. From comparisons between the computational results and the experimental data, the validity of the mathematical formula for the blade forces was examined and good results were obtained qualitatively. Hence, we can get the flow characteristics of multi-blade centrifugal fan and it will be a corner stone of the development of the multiblade centrifugal fan.

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Design Optimization of a Printed Circuit Heat Exchanger Using Surrogate Models (대리모델들을 이용한 인쇄형 열교환기의 최적설계)

  • Lee, Sang-Moon;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.14 no.5
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    • pp.55-62
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    • 2011
  • Shape optimization of a Printed circuit heat exchanger (PCHE) has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (3-D RANS) analysis and surrogate modeling techniques. The objective function is defined as a linear combination of effectiveness of the PCHE term and pressure drop in the cold channels of the PCHE. The cold channel angle and the ellipse aspect ratio of the cold channel are used as design variables for the optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results of three types of surrogate model are compared each other. The results of the optimizations indicate improved performance in friction loss but low performance in effectiveness than the reference shape.

DESIGN OPTIMIZATION OF UPPER PLENUM OF PBMR USING RESPONSE SURFACE APPROXIMATION (반응면기법을 이용한 PBMR 기체냉각형 고온가스로 상층부의 최적설계)

  • Lee, S.M.;Kim, K.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.187-194
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    • 2010
  • Shape optimization of an upper plenum of PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of eight of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

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DESIGN OPTIMIZATION OF UPPER PLENUM OF PBMR USING RESPONSE SURFACE APPROXIMATION (반응면기법을 이용한 PBMR 기체냉각형 고온가스로 상층부의 최적설계)

  • Lee, S.M.;Kim, K.Y.
    • Journal of computational fluids engineering
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    • v.15 no.3
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    • pp.16-23
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    • 2010
  • Shape optimization of an upper plenum of a PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of height of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

Hybrid RANS/LES Method for Turbulent Channel Flow (채널난류유동에 대한 하이브리드 RANS/LES 방법)

  • Myeong, Hyeon-Guk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.8
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    • pp.1088-1094
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    • 2002
  • A channel flow with a high Reynolds number but coarse grids is numerically studied to investigate the prediction possibility of its turbulence which is three-dimensional and time-dependent. In the present paper, a Reynolds-Averaged Navier-Stokes (RANS) model, a Large Eddy Simulation (LES) and a Navier-Stokes equation with no model are tested with a new approach of hybrid RANS/LES, which reduces to RANS model in the boundary layers and at separation, and to Smagorinsky-like LES downstream of separation, and then compared with each other. It is found that the simulations of hybrid RANS/LES method sustain turbulence like those of LES and with no model, and the results are stable and fairly accurate. This indicates strongly that gradual improvements could lead to a simple, stable, and accurate approach to predict turbulence phenomena of wall-bounded flow.

Design Optimization of A Multi-Blade Centrifugal Fan with Navier-Stokes Analysis and Response Surface Method (삼차원 Navier-Stokes 해석과 반응면기법을 이용한 원심다익송풍기의 최적설계)

  • Seo, Seoung-Jin;Kim, Kwang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.10
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    • pp.1457-1463
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    • 2003
  • In this paper, the response surface method using three-dimensional Navier-Stokes analysis to optimize the shape of a multi-blade centrifugal fan, is described. For numerical analysis, Reynolds-averaged Navier-Stokes equations with standard k - c turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in this centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Linear Upwind Differencing Scheme(LUDS) is used to approximate the convection terms in the governing equations. SIMPLEC algorithm is used as a velocity-pressure correction procedure. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time.

Design Optimization of A Multi-Blade Centrifugal Fan with Navier-Stokes Analysis (삼차원 Navier-Stokes 해석을 이용한 원심다익송풍기의 최적설계)

  • Seo, Seoung-Jin;Kim, Kwang-Yong
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.2157-2161
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    • 2003
  • In this paper, the response surface method using three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved blades centrifugal fan, is described. For numerical analysis, Reynolds-averaged Navier-Stokes equations with standard k-e turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in forward-curved blades centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Linear Upwind Differencing Scheme(LUDS) is used to approximate the convection terms in the governing equations. SIMPLEC algorithm is used as a velocity-pressure correction procedure. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time

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HEAT-TRANSFER ANALYSIS OF A COOLING CHANNEL WITH INCLINED ELLIPTICAL DIMPLES (기울어진 타원형 딤플이 부착된 냉각 유로에 대한 열전달 성능해석)

  • Kim, H.M.;Moon, M.A.;Kim, K.Y.
    • Journal of computational fluids engineering
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    • v.17 no.1
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    • pp.1-7
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    • 2012
  • This paper deals with a parametric study on inclined elliptical dimples to enhance heat transfer in a channel. Three-dimensional Reynolds-averaged Naiver-Stokes equations are solved to estimate flow and heat transfer in dimpled channel. As turbulence closure, the low-Re shear stress transport model is employed. Two non-dimensional geometric variables, dimple ellipse diameter ratio and angle of main diameter to flow direction are selected for the parametric study. The inclined elliptical dimples show higher heat-transfer performance but with higher pressure drop compared to the circular dimples. And there is an optimum inclination angle that gives the maximum heat transfer.

Assessment of Optimization Methods for Design of Axial-Flow Fan (축류송풍기 설계를 위한 최적설계기법의 평가)

  • Choi, Jae-Ho;Kim, Kwang-Yong
    • 유체기계공업학회:학술대회논문집
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    • 1999.12a
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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.

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