• Title/Summary/Keyword: SST 난류모델

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Computation of Oscillating Airfoil Flows with SST Turbulence Model (SST 난류 모델을 이용한 진동하는 익형 주위의 유동장 해석)

  • Lee Bo-sung;Lee Sangsan;Lee Dong Ho
    • 한국전산유체공학회:학술대회논문집
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    • 1999.05a
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    • pp.131-136
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    • 1999
  • 박리를 수반하는 진동하는 이차원 익형 주위의 비정상 유동장에 대해 SST 난류 모델을 이용하여 해석을 수행하였다. SST 모델은 정상 유동장 해석에서 기존의 난류 모델에 비해 우수한 성능을 보인다고 알려져 있으나 큰 박리영역에서 공력 계수의 진동 현상을 보이는 등 비정상 유동장 해석에 문제점을 보이고 있다. 본 논문에서는 이러한 공력 계수의 진동 현상이 SST 모델을 이차원으로 확장하는 과정에서 발생한 것임을 밝히고 이에 대한 보완을 통하여 수정된 SST 모델을 제시하고자 한다. SST 모델의 기본이 되었던 BSL 모델 및 SST 모델, 수정된 SST 모델을 사용하여 정상 유동장과 비정상 유동장 해석을 수행하여 각 모델의 난류 유동장 해석 특성을 비교하고 이를 통하여 수정된 SST 모델이 박리를 수반하는 비정상 유동장 해석에서 원래의 SST 모델에 비해 향상된 결과를 나타남을 알 수 있었다.

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Modification of SST Turbulence Model for Computation of Oscillating Airfoil Flows (진동하는 익형 주위의 유동장 해석을 위한 SST 난류 모델의 수정)

  • Lee Bo-sung;Lee Sangsan;Lee Dong Ho
    • Journal of computational fluids engineering
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    • v.4 no.3
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    • pp.44-51
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    • 1999
  • A modified version of SST turbulence model is suggested to simulate unsteady separated flows over oscillating airfoils. The original SST model, which shows good performance in predicting various steady flows, often results in oscillatory behavior of aerodynamic loads in large separated flow regions. It is shown that this oscillatory behavior is due to the adoption of the absolute value of vorticity in generalizing the original model. As a remedy, a modification is made such that the vorticity in the original SST model is replaced by strain rate. The present model is verified for a mild separated airfoil flow at fixed angle of incidence and for unsteady flowfields about oscillating airfoils. The results are compared with BSL model and original SST model. It is illustrated that the present model gives a better agreement with the experimental results than other two models.

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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.

Numerical Simulation of Square Cylinder Near a Wall with the ε -SST Turbulence Model (ε -SST 난류 모델을 적용한 벽면 근처 정사각주 유동장의 수치 해석)

  • Lee,Bo-Seong;Kim,Tae-Yun;Park,Yeong-Hui;Lee,Dong-Ho
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.8
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    • pp.1-7
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    • 2003
  • The numerical simulation of flow-filed around a square cylinder near a wall with $\varepsilon$-SST turbulence model is carried out in this study. The newly suggested $\varepsilon$-SST turbulence model that modifies the original SST turbulence model is proved to yield more accurate results than the other 2-equation turbulence models in large separation region around a bluff body. Therefore, $\varepsilon$-SST turbulence model can be effectively applied for predicting the flow-fields with large separation. And it is found that vortex shedding is suppressed below the critical gap height, the Strouhal number is affected by the gap height and the wall boundary layer thickness.

Numerical Analysis of Thermal and Flow affected by the variation of rib interval and Pressure drop Characteristics (리브 간격 변화에 따른 열.유동 수치해석 및 압력 저하 특성)

  • Chung, Han-Shik;Lee, Gyeong-Wan;Shin, Yong-Han;Choi, Soon-Ho;Jeong, Hyo-Min
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.5
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    • pp.616-624
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    • 2011
  • The flow characteristics and heat transfer augment on the periodically arranged semi-circular ribs in a rectangular channel for turbulent flow has been investigated numerically. The aspect ratio of the rectangular channel was AR=5, the rib height to hydraulic diameter ratio were 0.07 and rib height to channel height ratio was set as e/H=0.117 for various PR(rib pitch-to-rib height rate) between 8~14, respectively. The SST k-${\omega}$ turbulence model and v2-f turbulence model were used to find out the heat transfer and the flow characteristics of near the wall which are suited to obtain realistic phenomena. The numerical analysis results show turbulent flow characteristics, heat transfer enhancement and friction factor as observed experimentally. The results predict that turbulent kinetic energy(k) is closely relative to the diffusion of recirculation flow. and v2-f turbulence model simulation results have a good agreement with experimental values.

Compressibility Correction Effects of Two-equation Turbulence Models for a Supersonic Through-type Pintle Nozzle with Large Scale Separation Flow (큰 박리유동을 동반한 초음속 관통형 핀틀노즐 유동에 적합한 2-방정식 난류모델의 압축성계수 보정 영향)

  • Heo, Junyoung;Jung, Junyoung;Sung, Hong-Gye;Yang, June-Seo;Lee, Ji-Hyung
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.1
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    • pp.61-69
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    • 2013
  • Numerical simulations have been performed for assessment of compressibility correction of two-equation turbulent models suitable for large scale separation flows perturbed by a pintle strokes. Two-equation turbulence models, the low Reynolds k-${\varepsilon}$ and the k-${\omega}$ SST models with or without compressibility correction proposed by Wilcox and Sarkar are evaluated. The detail flow structures are observed and static pressures along nozzle wall are compared with experimental results. Mach disk location and pressure recovery profiles in flow separation region are noticeably distinct between turbulent models of k-${\varepsilon}$ and k-${\omega}$ SST. The compressible effect corrections to those models improve resolving of separation flow behaviors. The compressibility corrections to k-${\varepsilon}$ model have provided very comparable results with test data.

EVALUATION OF TURBULENCE MODELS FOR ANALYSIS OF THERMAL STRIPING (Thermal Striping 해석 난류모델 평가)

  • Cho, Seok-Ki;Kim, Se-Yun;Kim, Seong-O
    • Journal of computational fluids engineering
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    • v.10 no.4 s.31
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    • pp.1-11
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    • 2005
  • A numerical study of the evaluation of turbulence models for thermal striping phenomenon is performed. The turbulence models chosen in the present study are the two-layer model, the shear stress transport (SST) model and the V2-f model. These three models are applied to the analysis of the triple-jet flow with the same velocity but different temperatures. The unsteady Reynolds-averaged Navier-Stokes (URANS) equation method is used together with the SIMPLEC algorithm. The results of the present study show that the temporal oscillation of temperature is predicted by the SST and V2-f models, and the accuracy of the mean velocity, the turbulent shear stress and the mean temperature is a little dependent on the turbulence model used. In addition, it is shown that both the two-layer and SST models have nearly the same capability predicting the thermal striping, and the amplitude of the temperature fluctuation is predicted best by the V2-f model.

Capability of Turbulence Modeling Schemes on Estimating the Film Cooling at Parallel Wall Jet-Nozzle Configuration (평행 벽 제트-노즐 형상에서 난류모델별 막냉각 예측 능력)

  • Lee, Jun;Kim, Yoo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.13 no.1
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    • pp.10-18
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    • 2009
  • Numerical simulation has been performed in this study to investigate the capabilities of turbulence modeling schemes on estimating the film cooling at a referenced parallel wall jet-nozzle configuration. Also a additional simulation has been performed for film cooling under 2-dimensional axis symmetry conditions at a parallel wall jet-nozzle configuration. It was concluded that the best turbulence model is the standard $k-{\epsilon}$ model with enhanced wall functions. Also a additional simulation showed the film cooling characteristics that are resonable physically.

Verification and Validation of the Numerical Simulation of Transverse Injection Jets using Grid Convergence Index (GCI 를 이용한 수직분사제트 수치모사의 검증 및 확인)

  • 원수희;정인석;최정열
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.4
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    • pp.53-62
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    • 2006
  • Two-dimensional steady flowfields generated by transverse injection jets into a supersonic mainstream are numerically simulated. Fine-scale turbulence effects are represented by a k-${\omega}$ SST two-equation closure model which includes $y^+$ effects on the turbulence model. Solution convergence is evaluated by using Grid Convergence Index(GCI), a measure of uncertainty of the grid convergence. Comparison is made with experimental data and other turbulence models in term of surface static pressure distributions, the length of the upstream separation region, and the penetration height. Results indicate that the k-${\omega}$ SST model correctly predicts the mean surface pressure distribution and the upstream separation length for low static pressure ratios. However, the numerical predictions become less consistent with experimental results as the static pressure ratio increases. All these results are taken within 1% error band of grid convergence.

Assessment of Turbulence Models with Compressibility Correction for Large Flow Separation in a Supersonic Convergent-Divergent Rectangular Nozzle (강한 박리 유동을 동반한 초음속 수축-확장 사각 노즐 유동에 적합한 난류 모델과 압축성 보정 모델의 평가)

  • Lee, Juyong;Shin, Junsu;Sung, Hong-Gye
    • Journal of Aerospace System Engineering
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    • v.12 no.5
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    • pp.40-47
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    • 2018
  • The objective of this study is to investigate the turbulence models with compressibility correction for large separation-flow in a supersonic convergent-divergent rectangular nozzle. As turbulence models, Yang and Shih's Low-Re $k-{\varepsilon}$ model, Mener's $k-{\omega}$ SST model and Wilcox's $k-{\omega}$model were evaluated. In order to get a significant compressible effects, Sarkar and Wilcox compressibility correction models were applied to the turbulence models respectively. Also, the simulation results were compared with experimental data. The turbulence model with compressibility correction model improves both of shock position and pressure recovery, but deteriorates the length of Mach disk.