• Title, Summary, Keyword: RANS equation

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Influence of the Leading Edge Shape of a 2-Dimensional hydrofoil on Cavitation Characteristics (2차원 날개단면의 앞날 형상 변화에 따른 캐비테이션 특성 연구)

  • I.H. Song;J.W. Ahn;I.S. Moon;K.S. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.37 no.1
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    • pp.60-66
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    • 2000
  • In order to improve cavitation characteristics for a high-speed propeller, leading edge shape of a 2-D hydrofoil is investigated numerically and experimentally. For flowfield analysis around the leading edge, the incompressible Reynolds Averaged Navier-Stokes(RANS) equation is solved using the standard $k-\varepsilon$ turbulence model and a finite volume method(FVM). The cavitation thickness, which is occurred on hydrofoil surface, is predicted using the panel code. It is shown that the calculation codes predict the experimental trend fairly well. From these results, new hydrofoils are designed

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Unsteady Flow Analysis Around a HAWT System Using Sliding Mesh Technique (미끄럼 격자를 이용한 HAWT 시스템 주위의 비정상 유동장 해석)

  • Lee, Chi-Hoon;Kim, Sang-Gon;Joh, Chang-Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.3
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    • pp.201-209
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    • 2011
  • An unsteady RANS analysis study of the 3-D flow around the NREL Phase VI horizontal axis wind turbine(HAWT) was performed using sliding mesh approach. Two different analysis models such as rotor-only and rotor with tower/nacelle were constructed to investigate the blade/tower interaction. Analysis results for the rotor with tower/nacelle were compared with the corresponding NREL's experimental data which produced fairly good validation of the present CFD model. Comparison of flows around those two models also clearly showed the blade/tower interaction even it was small for upwind configuration. Other visualization results and integrated aerodynamic loads including torque of the blade demonstrated the effective unsteady flow simulation capability of the present CFD model.

Performance Prediction a 10MW-Class Wind Turbine Blade Considering Aeroelastic Deformation Effect (공탄성 변형효과를 고려한 10MW급 풍력발전기 블레이드의 성능해석)

  • Kim, Dong-Hyun;Kim, Yo-Han;Ryu, Gyeong-Joong;Kim, Dong-Hwan;Kim, Su-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.657-662
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    • 2011
  • In this study, aeroelastic performance analyses have been conducted for a 10MW class wind turbine blade model Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate detailed dynamic responsed of wind turbine blade Reynolds-averaged Navier-Stokes (RANS) equations with k-${\omega}$ SST turbulence model are solved for unsteady flow problems of the rotating turbine blade model. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D turbine blade for fluid-structure interaction (FSI) problems.

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Internal Flow characteristics of Ramjet Supersonic Intake (램제트 초음속 흡입구 내부 유동 특성)

  • Lee, Hyoung-Jin;Kim, Sei-Hwan;Jeung, In-Seuck
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.331-334
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    • 2011
  • The performance of ramjet engine is closely associated with a supersonic intake. In this study, experiments and computational simulations were conducted to observe the internal flow characteristics of the supersonic intake. The supersonic intake which have self-starting characteristics was designed and manufactured. The flow characteristics was analyzed from the experimental results using the supersonic wind tunnel testing and computational results using RANS equation and Menter's SST turbulence model. The detailed visualization results were suggested for the pseudo-shock wave of stable operations and for the inlet buzz phenomenon of unstable operations.

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Large Eddy Simulation for the Analysis of Practical Combustion Field (실용 연소장 해석을 위한 대 와동 모사)

  • Hwang, Cheol-Hong;Lee, Chang-Eon
    • 한국연소학회:학술대회논문집
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    • pp.181-188
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    • 2005
  • Large eddy simulation(LES) methodology used to model the isothermal swirling flows in a dump combustor and the turbulent premixed flame in a model gas turbine combustor. The LES solver was implemented on parallel computer consisting 16 processors. In isothermal flow simulation, the results was compared with that of ${\kappa}-{\varepsilon}$ model as well as experimental data, in order to verify the capability of LES code. To model the turbulent premixed flame in a gas turbine, the G-equation flamelet model was used. The results showd that LES and RANS well predicted the mean velocity field of a non-swirling flow. However, in swirling flow, LES showed a better performance in predicting the mean axial and azimuthal velocities, and the central recirculation zone than those of RANS. In a model gas turbine combustor, the operation condition of high pressure and temperature induced the different phenomena, such as flame length and flow-field information, comparing with the condition of ambient pressure and temperature. Finally, it was identified that the flame and heat release oscillations are related to the vortex shedding generated by swirl flow and pressure wave propagation.

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Assessment and Validation of Turbulence Models for the Optimal Computation of Supersonic Nozzle Flow (초음속 노즐 유동의 최적해석을 위한 난류모델의 평가와 선정)

  • Kam, Ho Dong;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.1
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    • pp.18-25
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    • 2013
  • Assessment and validation of RANS turbulence models are conducted for the optimal analysis of supersonic converging-diverging nozzle through the comparison between computational results and experimental data. One/two equation turbulence closures such as Spalart-Allmaras, RNG k-${\varepsilon}$, and k-${\omega}$ SST are employed to simulate the two-dimensional nozzle flow. Computational results with the turbulence models mentioned fairly well predict shock structure of the nozzle-inside and pressure distribution along the wall. Especially, SST model among the employed ones shows the best agreement to experimental results.

Robustness Improvement and Assessment of EARSM k-ω Model for Complex Turbulent Flows

  • Zhang, Qiang;Li, Dian;Xia, ZhenFeng;Yang, Yong
    • International Journal of Aerospace System Engineering
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    • v.2 no.2
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    • pp.67-72
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    • 2015
  • The main concern of this study is to integrate the EARSM into an industrial RANS solver in conjunction with the $k-{\omega}$ model, as proposed by Hellsten (EARSMKO2005). In order to improve the robustness, particular limiters are introduced to turbulent conservative variables, and a suitable full-approximation storage (FAS) multi-grid (MG) strategy is designed to incorporate turbulence model equations. The present limiters and MG strategy improve both robustness and efficiency significantly but without degenerating accuracy. Two discretization approachs for velocity gradient on cell interfaces are implemented and compared with each other. Numerical results of a three-dimensional supersonic square duct flow show that the proper discretization of velocity gradient improves the accuracy essentially. To assess the capability of the resulting EARSM $k-{\omega}$ model to predict complex engineering flow, the case of Common Research Model (CRM, Wing-Body) is performed. All the numerical results demonstrate that the resulting model performs well and is comparable to the standard two-equation models such as SST $k-{\omega}$ model in terms of computational effort, thus it is suitable for industrial applications.

Numerical Design and Performance Prediction of Low Specific Speed Centrifugal Pump Impeller

  • Yongxue, Zhang;Xin, Zhou;Zhongli, Ji;Cuiwei, Jiang
    • International Journal of Fluid Machinery and Systems
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    • v.4 no.1
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    • pp.133-139
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    • 2011
  • In this paper, Based on Two-dimensional Flow Theory, adopting quasi-orthogonal method and point-by-point integration method to design the impeller of the low specific speed centrifugal pump by code, and using RANS (Reynolds Averaged N-S) Equation with a standard k-${\varepsilon}$ two-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the impeller of the low specific speed pump. An analysis of the influences of the blade profile on velocity distributions, pressure distributions and pump performance and the investigation of the flow regulation pattern in the impeller of the centrifugal pump are presented. And the result shows that this method can be used as a new way in low speed centrifugal pump impeller design.

CAVITATION FLOW ANALYSIS OF 2-D HYDROFOIL USING A HOMOGENEOUS MIXTURE MODEL ON UNSTRUCTURED MESHES (비정렬 격자계에서 균질혼합 모델을 이용한 2차원 수중익형 주위의 캐비테이션 유동 해석)

  • An, S.J.;Kwon, O.J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.20-24
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    • 2011
  • In this paper, numerical simulation of cavitation flow for modified NACA66 hydrofoil was made by using the multi-phase RANS equation based on pseudo-compressibility. The Homogeneous mixture model comprised of the mixture continuity, mixture momentum and liquid volume fraction equations was utilized. A vertex-centered finite-volume method was used in conjunction 2nd-order Roe's FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing The Spalart-Allmaras one equation model was employed for the closure of turbulence. Reasonable agreements were obtained between the calculation results and the experiment for pressure coefficients on the hydrofoil surface.

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Analysis of Hydraulic effect on Removing Side Overflow Type Structures in Woo Ee Stream Basin (우이천 유역의 횡단 월류형 구조물 철거에 의한 수리영향 분석)

  • Moon, Young-Il;Yoon, Sun-Kwon;Chun, Si-Young;Kim, Jong-Suk
    • 한국방재학회:학술대회논문집
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    • pp.687-690
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    • 2008
  • Currently, Stream flow analysis has been accomplished by one or two dimensional equations and was applied by simple momentum equations and fixed energy conservations which contain many reach uppermost limit. In this study, FLOW-3D using CFD(Computational Fluid Dynamics) was applied to stream flow analysis which can solve three dimensional RANS(Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behavior and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as $k-\varepsilon$, RNG(Renomalized Group Theory) $k-\varepsilon$ and LES(Large Eddy Simulation). Numerical analysis results have been illustrated by the turbulence energy effects, velocity of flow, water level pressure and eddy flows around the side overflow type structures at Jangwall bridge in urban stream.

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