• Title/Summary/Keyword: RSM turbulent model

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Numerical analysis of a turbulent boundary layer with pressure gradient using Reynolds-transport turbulence model (레이놀즈 응력모델을 이용한 압력구배가 있는 난류경계층의 유동장 해석)

  • Lee, Seong-Hyeok;Yu, Hong-Seon;Choe, Yeong-Gi
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.3
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    • pp.280-293
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    • 1998
  • Numerical study on turbulent and mean structures of a turbulent boundary layer with longitudinal and spanwise pressure gradient is carried out by using Reynolds-stress-model (RSM). The existence of pressure gradient in a turbulent boundary layer causes the skewing or divergence of rates of strain, which contributes to production of turbulent kinetic energy. Also, this augmentation of production due to extra rates of strain can increase the turbulent mixing and cause the anisotropy of turbulent intensities in the outer layer. This paper uses the Reynolds Stress Model to capture anisotropy of turbulent structures effectively and is devoted to compare the results computed by using RSM and the standard k-.epsilon. model with experimental data. It is concluded that the RSM can produce the more accurate predictions for capturing the anisotropy of turbulent structure than the standard k-.epsilon. model.

Assessment of Reynolds Stress Model for the Analysis of Floating Flames in Stagnating Flows (정체유동에서의 난류 부상 화염 해석을 위한 Reynolds 응력 모델의 검증)

  • Im, Yong-Hoon;Huh, Kang-Yul
    • Journal of the Korean Society of Combustion
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    • v.7 no.2
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    • pp.49-61
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    • 2002
  • Numerical simulation is performed for stagnating turbulent flows of impinging and countercurrent jets by the Reynolds stress model(RSM). Results are compared with those of the ${\kappa}-{\varepsilon}$ model and available data to assess the flow characteristics and turbulence modes. Three variants of the RSM tested are those of Gibson and Launder(GL), Craft and Launder(GL-CL) and Speziale, Sarkar and Gatski(SSG). As well known, the ${\kappa}-{\varepsilon}$ model overestimates turbulent kinetic energy near the wall significantly. Although the RSM is superior to the ${\kappa}-{\varepsilon}$ model, it shows considerable difference according to how the redistributive pressure-strain term is modeled. Results of the RSM for countercurrent jets are improved with the modified coefficients for the dissipation rate, $C_{{\varepsilon}1}\;and\;C_{{\varepsilon}2}$ suggested by Champion and Libby. The performance of the three variants of the RSM model for stagnating flows are assessed.

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Investigation of the Prediction Performance of Turbulence and Combustion Models for the Turbulent Partially-premixed Jet Flame (난류 부분예혼합 제트화염에 대한 난류 및 연소모델의 예측성능 검토)

  • Kim, Yu Jeong;Oh, Chang Bo
    • Fire Science and Engineering
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    • v.28 no.4
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    • pp.35-43
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    • 2014
  • The prediction performance of 9 model sets, which combine 3 turbulent models and 3 combustion models, was investigated numerically for turbulent partially-premixed jet flame. The standard ${\kappa}-{\varepsilon}$ (SKE), Realizable ${\kappa}-{\varepsilon}$ (RKE) and Reynolds stress model (RSM) were used as a turbulence model, and the eddy dissipation concept (EDC), steady laminar flamelet (SLF) and unsteady laminar flamelet model (ULF) were also adopted as a combustion model. The prediction performance of those 9 model sets was evaluated quantitatively and qualitatively for Sandia D flame of which flame structure was measured precisely. The flame length was predicted as, from longest to shortest, RSM > SKE > RKE, and the RKE predicted the flame length of the jet flame much shorter than experiment. The flame temperature was over predicted by the combination of RSM + SLF or RSM + ULF while the flame length obtained by RSM + SLF and RSM + ULF was well agreed with the experiment. The combination of SKE + SLF and SKE + ULF predicts well the flame length as well as the temperature distribution. The SKE turbulence model was most superior to the other turbulent models, and SKE + ULF showed the best prediction performance for the structure of turbulent partially-premixed jet flame.

A study on the three dimensional turbulent flow analysis of wake flow behind rotating blade row between hub and midspan (허브와 중앙스팬 사이의 회전익 후류 3차원 난류유동해석에 관한 연구)

  • No, Su-Hyeok;Jo, Gang-Rae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.7
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    • pp.911-918
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    • 1997
  • The turbulent viscous wake flows behind a single airfoil, two-dimensional stationary blade row and three-dimensional rotating blade row were calculated, and the numerical results were compared with experimental ones. The numerical technique was based on the SIMPLE algorithm using three turbulent closure models, standard k-.epsilon. model(WFM), low Reynolds number k-.epsilon. model(LRN) and Reynolds stress model (RSM). In the case of a single airfoil, WFM, LRN and RSM presented fairly good velocity distributions in the wake compared with experimental data. In the case of the stationary blade row, LRN and RSM presented better results than WFM for wake velocity distribution, and especially LRN showed best results among these three turbulent models. In the case of the rotating blade row, WFM and LRN showed fairly good agreement with experimental data of the three-dimensional velocity component distributions in the range from hub to mid span region. LRN was also superior to WFM in accuracy of prediction for the wake velocity distribution as same with the cases of a airfoil and the stationary blade row.

Numerical Simulation of Turbulent Flows Under a Plane Rate of Strain Condition in a Rotating $90^{\circ}$ Curved Duct (평면변형율 조건 하의 회전하는 $90^{\circ}$ 곡덕트 내 난류유동의 전산해석)

  • Kwon, Hyung-Joong;An, Jung-Soo;Choi, Young-Don
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.485-490
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    • 2000
  • The effect of curvature, rotation, variable cross-section can make very complex flow pattern in turbo-machinery such as Pumps, compressors, turbines, In this study of turbulent flow characteristics rotating $90^{\circ}$ curved duct under a Plane rate of strain condition is computationally analyzed. The objective of this study is to understand the complex turbulent flow phenomena in turbo-machinery passage by analyzing the modeled rotating $90^{\circ}$ curved duct flow. RSM(Reynolds Stress Model) was employed for the turbulence modeling of Reynolds stress in momentum equations proposed by Shin(1995). The three dimensional computational code which adopts RSM for trubulence modeling was newly developed for the generalized curvilinear coordinate.

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Turbulent Flow through a Rotating Curved Duct with Reynolds Stress Model to Automatically Sencer the Presence of a Wall (벽면감지장치를 가지는 RSM에 의한 회전하는 곡관 내 난류유동)

  • Chun, Kun-Ho;Kim, Dong-Chul;Choi, Young-Don
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.473-478
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    • 2000
  • In this study, the characteristics of the three-dimensional turbulent flow in a rotating square sectioned $90^{\circ}$ bend were investigated by numerical simulation and experiment. In the experimental study, the characteristics of a developing turbulent flow are measured using hot-wire anemometer to seize the rotational effects on the flow characteristics and to compare the results of computational simulation with Reynolds stress model. Each refinement is shown to lead to an appreciable improvement in the agreement between measurement and computation.

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A Numerical Study on the Turbulent Flow in the Discharge Flow Path from a Diffuser to a Wall (디퓨저에서 벽면으로의 방출유로에서의 난류유동에 관한 수치 해석적 연구)

  • Lee J.;Kim Y. I.
    • 한국전산유체공학회:학술대회논문집
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    • 2001.10a
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    • pp.44-50
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    • 2001
  • A numerical study was made to choose the better turbulence model for the flow in the discharge flow path from a diffuser to a wall. In this study standard $\kappa-\epsilon$ model(SKE), RNG $\kappa-\epsilon$ model(RNG), and Reynolds stress model(RSM) were applied. In case of the flow with relatively high Reynolds number at a diffuser inlet, the pressure loss coefficients by RNG have a tendency to be near to those by SKE at small ratio(below about 0.35) of $h/D_o$, but to those by RSM at large ratio(above about 0.35). At large ratio RNG begins to enlarge the effects of rapid strain and streamline curvature. RNG & RSM are recommended as the appropriate turbulence models for this case. But it is noticeable that the velocity gradient pattern in RNG is same as in SKE, and also that the total pressure distribution in RNG is same as in RSM only at swirling flow area, same as in SKE only at main flow area.

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A comparative investigation of the TTU pressure envelope -Numerical versus laboratory and full scale results

  • Bekele, S.A.;Hangan, H.
    • Wind and Structures
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    • v.5 no.2_3_4
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    • pp.337-346
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    • 2002
  • Wind tunnel pressure measurements and numerical simulations based on the Reynolds Stress Model (RSM) are compared with full and model scale data in the flow area of impingement, separation and wake for $60^{\circ}$ and $90^{\circ}$ wind azimuth angles. The phase averaged fluctuating pressures simulated by the RSM model are combined with modelling of the small scale, random pressure field to produce the total, instantaneous pressures. Time averaged, rsm and peak pressure coefficients are consequently calculated. This numerical approach predicts slightly better the pressure field on the roof of the TTU (Texas Tech University) building when compared to the wind tunnel experimental results. However, it shows a deviation from both experimental data sets in the impingement and wake regions. The limitations of the RSM model in resolving the intermittent flow field associated with the corner vortex formation are discussed. Also, correlations between the largest roof suctions and the corner vortex "switching phenomena" are observed. It is inferred that the intermittency and short duration of this vortex switching might be related to both the wind tunnel and numerical simulation under-prediction of the peak roof suctions for oblique wind directions.

Comparison of Two-Equation Model and Reynolds Stress Models with Experimental Data for the Three-Dimensional Turbulent Boundary Layer in a 30 Degree Bend

  • Lee, In-Sub;Ryou, Hong-Sun;Lee, Seong-Hyuk;Chae, Soo
    • Journal of Mechanical Science and Technology
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    • v.14 no.1
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    • pp.93-102
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    • 2000
  • The objective of the present study is to investigate the pressure-strain correlation terms of the Reynolds stress models for the three dimensional turbulent boundary layer in a $30^{\circ}$ bend tunnel. The numerical results obtained by models of Launder, Reece and Rodi (LRR) , Fu and Speziale, Sarkar and Gatski (SSG) for the pressure-strain correlation terms are compared against experimental data and the calculated results from the standard k-${\varepsilon}$ model. The governing equations are discretized by the finite volume method and SIMPLE algorithm is used to calculate the pressure field. The results show that the models of LRR and SSG predict the anisotropy of turbulent structure better than the standard k-${\varepsilon}$ model. Also, the results obtained from the LRR and SSG models are in better agreement with the experimental data than those of the Fu and standard k-${\varepsilon}$ models with regard to turbulent normal stresses. Nevertheless, LRR and SSG models do not effectively predict pressure-strain redistribution terms in the inner layer because the pressure-strain terms are based on the locally homogeneous approximation. Therefore, to give better predictions of the pressure-strain terms, non-local effects should be considered.

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Validation of the Reynolds Stress Turbulence Models in Turbulent Jet Diffusion Flames (난류분류확산화염에 대한 레이놀즈응력모델의 적용성 검토)

  • 한지웅;이태우;이근오;이창언
    • Journal of the Korean Society of Safety
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    • v.11 no.3
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    • pp.66-74
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    • 1996
  • Numerical simulations were carried out using standard Reynolds stress turbulence model(LRR model) and modified RSM(Janicka model ) to validate these models in combustion flow fields. Two flames were selected for use as a benchmark data for model testing. One is a conventional jet diffusion flame that has the effect of suppression of turbulence by combustion. The other is a triple jet diffusion flame that designed to give high turbulence to the periphery of the flame and to remove the low Reynolds-number flow fields. As a result, it was found that the modification of standard RSM model is indispensable in the modelling of flames with low turbulence region. And it is also necessary to improve the existing modified models for the universal use.

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