• Title/Summary/Keyword: Spalart-Allmaras Model

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Turbulent flow fields analysis using CFDS scheme (CFDS기법을 이용한 난류 유동장 해석)

  • Moon S. M.;Lee J. S.;Kim C.;Rho O. H.;Hong S. K.
    • 한국전산유체공학회:학술대회논문집
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    • pp.51-59
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    • 2001
  • An evaluation of one zero-equation and two one-equation eddy viscosity-transport turbulence closure models as implemented CFDS(Characteristic Flux Difference Splitting ) code is presented herein. Comparisons of Baldwin-Lomax model as zero-equation and Baldwin-Barth and Spalart-Allmaras model as one-equation are presented for three test cases, first inlvolving the 3 dimensional supersonic flow at M=1.98 over tangent ogive cylinder, second involving the 2 dimensional transonic flow at M=0.79 over RAE 2822 airfoil, third involving the 3 dimensional transonic flow at M=0.84 over ONERA M6 wing. The numerical results of CFDS code will also examined through direct comparison with experimental data.

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An experimental study for developing of silencer to be adapted large gun (대구경 화포용 소음기 개발을 위한 실험적 연구)

  • Lee, Hae suk;Park, Sung ho;Kim, Sang min;Kang, Tae yeop;Kim, Heung soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.558-563
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    • 2014
  • To reduce the transmission of large gun-generated noise from the firing test range to the community, we have tested a silencer to be used with howitzer(155mm KM114A2) after simulation. Numerical analysis was conducted by using a commercial CFD code, FLUENT. To analyze complex blast flow fields, the Spalart-Allmaras model was applied under 2 dimensional and axisymmetric conditions. Firing tests were also performed with the KM114A2 howitzer while the silencer was installed. This paper describes a result of comparison between results of computer analysis and test outcomes which were gotten by firing 155mm projectiles at the testing range. This paper will also be informative to the muffler design which will be adapted to 155mm large gun in the future.

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Turbulence Modeling considering the Effects of Submerged Vegetation Flows (침수식생 흐름의 특성을 반영한 난류모델링)

  • Song, Youngdae;Lee, Seonmin;Choi, Sung-Uk
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.127-127
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    • 2017
  • 침수식생이 식재된 개수로에서 식생밀도에 따라 유동 및 난류의 특성이 변화된다. 이러한 특성은 식생에서의 유사, 영양물질, 용존 산소 등에 영향을 미치며 수중 생물의 서식에 변화를 준다. 따라서 침수식생이 식재된 개수로 흐름을 이해하는 것은 중요하게 여겨지고 있으며 많은 선행연구자들에 의해 실험 및 수치모의를 통해 활발히 연구되고 있다. 하지만 대부분의 RANS(Reynolds-Averaged Navier-Stokes)를 기반으로 한 선행연구에서는 침수식생의 흐름 특성을 반영하지 않은 모형을 이용하여 정확한 모의 결과를 도출하지 못 하였다. 이에 정확한 침수식생 흐름을 수치모의하기 위해서는 침수식생 흐름의 특성을 반영한 지배방정식을 이용해야 한다. 본 연구의 목적은 침수식생 흐름의 특성을 RANS 모형 중의 하나인 SA (Spalart-Allmaras) model에 반영하고, 식생밀도에 따른 유동 및 난류량을 실측치와 비교하는 것이다. RANS 방정식을 이용하여 난류모델링을 하였으며, 난류폐합문제를 해결하기 위해서 modified SA model을 이용하였다. 침수식생에서의 흐름을 해석하기 위해 운동량방정식에 식생항력을 추가하였다. 선행연구자의 식생수로 실험을 바탕으로 모형검증을 하였으며, 식생밀도에 따라 평균유속 및 난류구조를 확인하였다.

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Numerical study of CEDS scheme for turbulent flow (난류 유동장에 대한 CFDS 기법의 수치적 연구)

  • Moon Seong Mok;Kim Chongam;Rho Oh Hyun;Hong Seung Kyu
    • Proceedings of the KSME Conference
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    • pp.23-26
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    • 2002
  • An evaluation of one algebraic and two one-equation eddy viscosity-transport turbulence closure models as implemented to the CFDS(Characteristic Flux Difference Splitting) scheme is presented for the efficient computation of the turbulent flow. Comparisons of Baldwin-Lomax model as algebraic turbulence model and Baldwin-Barth and Spalart-Allmaras model as one-equation turbulence model are presented for three test cases for 3-dimensional flow. The numerical result of the CFDS schem is examined through comparison with the experimental data.

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Aeroacoustic Investigation of a Cavity with and without Doors by Delayed Detached Eddy Simulation

  • Liu, Yu;Tong, Mingbo
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.1
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    • pp.19-27
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    • 2015
  • In the present study, an effort was made to numerically investigate rectangular cavity aeroacoustics with and without doors. The simulation was performed on an open cavity with an aspect ratio of 5:1:1 at Mach 0.85 using the delayed detached eddy simulation (DDES) approach based on the Spalart-Allmaras model. Two cavity configurations, a clean cavity and a cavity with doors, were modeled. The results obtained from the clean cavity were compared with the experimental sound pressure levels (SPL) and the root mean square for the pressures applied. Furthermore, comparisons of frequencies were made using a modified semi-empirical Rossiter formula. The simulation using DDES precisely predicted the pressure fluctuation and the results matched the experiment quite well. The SPLs at the rear of the cavity were much higher than those in the front due to the instability of the shear layer impinging on the rear wall. Comparisons of DDES for the clean cavity and the doors-on cavity revealed that the SPLs inside the cavity as well as the magnitude of tones are amplified by the side doors. The main focus of this investigation was to obtain a better understanding of the open cavity acoustic resonance phenomenon and investigate the effects of cavity doors on the SPL.

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.

Performance Analysis of SITVC System with Various Secondary Injection Conditions (이차분사노즐 작동 조건 변화에 따른 SITVC 성능해석)

  • Bae, Ji-Yeul;Song, Ji-Woon;Kim, Tae-Hwan;Cho, Hyung-Hee;Bae, Ju-Chan
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.116-121
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    • 2011
  • Performance of Secondary Injection Thrust Vector Control system is investigated under various secondary injection operating conditions. 3-dimensional converging-diverging nozzle having 8 secondary injection nozzles is used in this numerical study. Total pressure of flow inside the nozzle is about 70bars, and total temperature set to 300K for cold flow simulation. Effect of secondary injection flow rate and injection nozzle configuration is considered in this research. Simulation is conducted with commercial CFD code Ansys Fluent v13. Spalart-Allmaras(1-equation)model is used for turbulence modeling with AUSM+ scheme. Various performance factors as Axial thrust, side force, system specific impulse ratio are considered and explained for system performance evaluation.

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COMPARISON OF TURBULENCE MODELS ON ANALYSIS OF AIRCRAFT CONFIGURATIONS AT TRANSONIC SPEED (천음속 영역에서 항공기 유동해석에 미치는 난류모델의 영향 비교)

  • Huh, J.;Lee, N.;Lee, S.;Kwak, E.
    • Journal of computational fluids engineering
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    • v.20 no.1
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    • pp.47-56
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    • 2015
  • In this paper, we study the effect of various turbulence models by comparing the aerodynamic characteristics and the flow patterns computed for aircraft models. An in-house CFD solver, MSAPv, that solves the three dimensional RANS equations with the turbulence model equations is used. The turbulence models used in this study are the Spalart-Allmaras model, Menter's $k-{\omega}$ SST model, Coakley's $q-{\omega}$ model, and Huang and Coakley's $k-{\varepsilon}$ model. DLR-F6 WB and WBNP configurations are selected for the study. We concentrate on the separated flow pattern variations with the turbulence models at the wing-body junction and the wing-pylon junction as well as drag polar curves.

THE STUDY ON THE SEPARATED FLOW OF A HUMP USING RANSMODELING (RANS 모델링을 이용한 Hump 형상의 박리 유동에 대한 연구)

  • Lee, J.;Bae, J.H.;Jung, K.J.
    • Journal of computational fluids engineering
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    • v.22 no.1
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    • pp.8-14
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    • 2017
  • In this paper, separated flow characteristics is studied using the RANS(Reynold-averaged Navier-Stokes) modeling. The analysis is performed for the NASA's hump configuration which is the combination of a flat plate and a hump. This configuration was used in NASA's flow control workshop and it was one of validation cases for RANS and LES simulations. The separation occurs at the 65% of model length where a slot is positioned for the flow control. No flow control case and steady suction case are studied using RANS modeling. The Spalart-Allmaras model and the SST(Shear Stress Transport) model are applied and their accuracy are compared. To correlate CFD analysis with experimental data, the optimal boundary condition was investigated and the effect of a cavity around the slot is studied for the no flow case.

Thrust performance at the various pintle shapes and positions (핀틀 형상 및 위치에 따른 추력 성능)

  • Kim, Joung-Keun;Lee, Ji-Hyung;Jang, Hong-Been
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.89-93
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    • 2008
  • The effect of pintle shapes and position to the thrust performance of Solid Rocket Motor was studied by experimental-aided Computational Fluid Dynamic(CFD). Among the turbulent models for RANS in Fluent, Spalart-Allmaras model was better agreement with the nozzle wall pressure distribution attained by cold-flow test than other models. When nozzle throat area was decreased, magnitude of thrust was increased. The bigger pintle size was, the more thrust of pintle tip pressure was obtained. Meanwhile the more thrust of nozzle and chamber pressure decreased. Hence, total thrust of big pintle was less than a small pintle under same throat area condition.

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