• Title/Summary/Keyword: 레이놀즈 평균 나비어 스톡스 방정식

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Effects of Stator Shroud Injection on the Aerodynamic Performance of a Single-Stage Transonic Axial Compressor (정익 슈라우드 공기분사가 단단 천음속 축류압축기의 공력성능에 미치는 영향)

  • Dinh, Cong-Truong;Ma, Sang-Bum;Kim, Kwang Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.1
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    • pp.9-19
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    • 2017
  • In this study, stator shroud injection in a single-stage transonic axial compressor is proposed. A parametric study of the effect of stator shroud injection on aerodynamic performances was conducted using the three-dimensional Reynolds-averaged Navier-Stokes equations. The curvature, length, width, and circumferential angle of the stator shroud injector and the air injection mass flow rate were selected as the test parameters. The results of the parametric study show that the aerodynamic performances of the single-stage transonic axial compressor were improved by stator shroud injection. The aerodynamic performances were the most sensitive to the injection mass flow rate. Further, the total pressure ratio and adiabatic efficiency were the maximum when the ratio of circumferential angle was 10%.

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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    • 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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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.

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.

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.

NUMERICAL STUDY ON DPS THRUSTER-HULL INTERACTION WITH DIFFERENT AXIS TILTING ANGLE (축기울기에 따른 DPS 스러스터와 선체의 상호간섭 수치해석)

  • Jin, D.-H.;Lee, S.-W.
    • Journal of computational fluids engineering
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    • v.21 no.1
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    • pp.72-77
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    • 2016
  • In this study, effects of thurster axis tilting angle on the thruster-hull interaction and propulsion performance in a dynamic positioning system of offshore plant are numerically investigated. Straight and 7-degree tilted downward thruster models as a form of ducted propeller are considered. For numerical simulations, Reynolds averaged Navier-Stokes equations with SST turbulence model are solved by using STAR-CCM+. Results show that thruster-hull interaction is reduced in 7-degree tilted thruster model with lower vortex strength between thruster and hull bottom, although the propulsion performance does not have noticeable difference in a bollard condition.

EFFECTS OF FLUIDIC OSCILLATOR GEOMETRY ON PERFORMANCE (유체진동기의 형상 변화가 성능에 미치는 영향)

  • Jeong, Han-Sol;Kim, Kwang-Yong
    • Journal of computational fluids engineering
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    • v.21 no.3
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    • pp.77-88
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    • 2016
  • A parametric study on a fluidic oscillator was performed numerically in this work. Three-dimensional unsteady Reynolds-averaged Navier-Stokes equations were solved to analyze the flow in the fluidic oscillator. As turbulence closure, $k-{\varepsilon}$ model was employed. Validation of the numerical results was performed by comparing numerical results with experimental data for frequency of the oscillation. The parametric study was performed using five geometric parameters. Performance of the fluidic oscillator was evaluated in terms of velocity ratio and pressure drop. The results show that the inlet channel width and the distance between splitters are important factors in determining the performance of the fludic oscillator.

Effects of Geometry of Anti-Vortex Holes on Film-Cooling Effectiveness (반와류 홀의 형상 변화가 막냉각 효율에 미치는 영향)

  • Kim, Jun-Hee;Kim, Sun-Min;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.17 no.2
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    • pp.12-23
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    • 2014
  • A parametric study on anti-vortex holes for turbine blade cooling was investigated numerically. Three-dimensional Reynolds-averaged Navier-Stokes equations and shear stress transport turbulence model were used for analysis of anti-vortex film cooling. Validation of numerical results was carried out comparing with experimental data. The cooling performance of anti-vortex holes was assessed by two geometric variables, the ratio of diameters of holes and the lateral distances between the primary hole and anti-vortex hole at blowing ratios of 0.5 and 1.0. The results showed that the spatially-averaged film-cooling effectiveness increases as the ratio of the diameters increases and the distance between the primary hole and anti-vortex hole decreases.

A Parametric Study on Inlet Duct Treatment for Improving the Operational Stability of a Centrifugal Compressor (운전안정성 향상을 위한 원심 압축기의 유입부 형상변화에 관한 연구)

  • Seo, Tae-Wan;Heo, Man-Woong;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.19 no.5
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    • pp.12-19
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    • 2016
  • In present study, a parametric study of a centrifugal compressor with inlet treatment has been performed numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport turbulence model was used for analysis of turbulence. The finite volume method and unstructured grid system were used for the numerical solution. Tested parameters were related to the geometry of the inlet duct. It was found that the application of circumferentially distributed holes in the inlet duct improves operational stability of the compressor compared to that with conventional inlet duct.

Effects of Geometry of a Boot-Shaped Rib on Heat Transfer and Pressure Drop (신발형 리브의 형상변화가 열전달 및 압력 강하에 미치는 영향)

  • Seo, Jae-Won;Kim, Jun-Hee;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.18 no.3
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    • pp.66-73
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    • 2015
  • This paper deals with a parametric study on boot-shaped ribs in a rectangular cooling channel. Numerical analysis of the flow and heat transfer was performed using three-dimensional Reynolds averaged Navier-Stokes equations with the Speziale, Sarkar and Gatski turbulence model. The parametric study was performed for the parameters, tip width-to rib width, tip height-to-rib height, rib height-to-channel height, and rib height-to-width ratios. To assess the cooling performance and friction loss, Numsselt number and friction factor were defined as the performance parameter, respectively. The results showed that the cooling performance and friction loss were seriously affected by the four geometric parameters.