• Title/Summary/Keyword: Detached-eddy simulation

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DETACHED EDDY SIMULATION OF BASE FLOW IN SUPERSONIC MAINSTREAM (초음속 유동장에서 기저 유동의 Detached Eddy Simulation)

  • Shin, J.R.;Won, S.H.;Choi, J.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.104-110
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    • 2008
  • Detached Eddy Simulation (DES) is applied to an axisymmetric base flow at supersonic mainstream. DES is a hybrid approach to modeling turbulence that combines the best features of the Reynolds-averaged Navier-Stokes RANS) and large-eddy simulation (LES) approaches. In the Reynolds-averaged mode, the model is currently based on either the Spalart-Allmaras (S-A) turbulence model. In the large eddy simulation mode, it is based on the Smagorinski subgrid scale model. Accurate predictions of the base flowfield and base pressure are successfully achieved by using the DES methodology with less computational cost than that of pure LES and monotone integrated large-eddy simulation (MILES) approaches. The DES accurately resolves the physics of unsteady turbulent motions, such as shear layer rollup, large-eddy motions in the downstream region, small-eddy motions inside the recirculating region. Comparison of the results shows that it is necessary to resolve approaching boundary layers and free shear-layer velocity profiles from the base edge correctly for the accurate prediction of base flows. The consideration of an empirical constant CDES for a compressible flow analysis may suggest that the optimal value of empirical constant CDES may be larger in the flows with strong compressibility than in incompressible flows.

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DETACHED EDDY SIMULATION OF BASE FLOW IN SUPERSONIC MAINSTREAM (초음속 유동장에서 기저 유동의 Detached Eddy Simulation)

  • Shin, J.R.;Won, S.H.;Choi, J.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.10a
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    • pp.104-110
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    • 2008
  • Detached Eddy Simulation (DES) is applied to an axisymmetric base flow at supersonic mainstream. DES is a hybrid approach to modeling turbulence that combines the best features of the Reynolds-averaged Navier-Stokes (RANS) and large-eddy simulation (LES) approaches. In the Reynolds-averaged mode, the model is currently based on either the Spalart-Allmaras (S-A) turbulence model. In the large eddy simulation mode, it is based on the Smagorinski subgrid scale model. Accurate predictions of the base flowfield and base pressure are successfully achieved by using the DES methodology with less computational cost than that of pure LES and monotone integrated large-eddy simulation (MILES) approaches. The DES accurately resolves the physics of unsteady turbulent motions, such as shear layer rollup, large-eddy motions in the downstream region, small-eddy motions inside the recirculating region. Comparison of the results shows that it is necessary to resolve approaching boundary layers and free shear-layer velocity profiles from the base edge correctly for the accurate prediction of base flows. The consideration of an empirical constant CDES for a compressible flow analysis may suggest that the optimal value of empirical constant CDES may be larger in the flows with strong compressibility than in incompressible flows.

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DETACHED EDDY SIMULATION OF AN INCOMPRESSIBLE FLOW PAST AN OPEN CAVITY (DES 방법을 이용한 비압축성 열린 공동 유동의 수치적 모사)

  • Chang K.S.;Park S.O.;Kwon O.J.;Constantinescu G.
    • Journal of computational fluids engineering
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    • v.10 no.3 s.30
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    • pp.48-54
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    • 2005
  • Three-dimensional incompressible flow past an open cavity in a channel is investigated using Detached Eddy Simulation(DES). The length to depth ratio of the cavity is 2 and the Reynolds number defined with the cavity depth is 3,360. The DES methods are based on the Menter's SST model. In the present work, two types of inflow conditions are used: one is RANS profile, the other is LES inflow from another Large Eddy Simulation(LES) of fully developed channel flow. The results are compared with experimental data and LES results in terms of the mean statistics, temporal physics and scalar transport phenomenon of the flow.

Detached Eddy Simulation of an incompressible flow past an open cavity (DES 방법을 이용한 비압축성 열린 공동 유동의 수치적 모사)

  • Chang K.S.;Park S.O.;Kwon O.J.;Constantinescu G.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.04a
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    • pp.148-152
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    • 2005
  • The three-dimensional incompressible flow past an open cavity in a channel is investigated using Detached Eddy Simulation(DES). The length to depth ratio of the cavity is 2 and the Reynolds number defined with the cavity depth is 3,360. The DES methods are based on the Mentor's SST model. In the present work, two types of inflow conditions are used; one is RANS profile, the other is LES inflow from another Large Eddy Simulation(LES) of fully developed channel flow. The results are compared with experimental data and LES results in terms of the mean statistics and temporal physics of the flow.

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Detached Eddy Simulation of Base Flow in Supersonic Mainstream (초음속 유동에서 기저유동의 Detached Eddy Simulation)

  • Shin, Jae-Ryul;Moon, Sung-Young;Won, Su-Hee;Choi, Jeong-Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.10
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    • pp.955-966
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    • 2009
  • DES method is applied to an axisymmetric base flow at supersonic mainstream. The model is based on the Spalart-Allmaras (S-A) turbulence model in the RANS mode, and is based on the subgrid scale model in the Large-eddy simulation (LES) mode. Accurate predictions of the base flowfield and base pressure are successfully achieved by using the DES methodology which is less expensive than LES. Flow properties at the edge of base, such as boundary layer thickness, momentum thickness and skin fraction are compared with Dutton et al [experimental data to proper prediction of base flowfiled. From the present results, The DES accurately resolves the physics of unsteady turbulent motions, such as shear layer rollup, large-eddy motions in the downstream region and small eddy motions inside the recirculating region. Moreover, The present results of using an empirical constant $C_{DES}$ of 1.2 shows good agreement with experimental data than conventional empirical constant $C_{DES}$ of 0.65.

Unsteady Three-Dimensional Analysis of Transverse Fuel Injection into a Supersonic Crossflow using Detached Eddy Simulation Part I : Non-Reacting Flowfield (DES를 이용한 초음속 유동내 수직 연료분사 유동의 비정상 3차원 해석 Part I : 비반응 유동장)

  • Won, Su-Hee;Jeung, In-Seuck;Choi, Jeong-Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.9
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    • pp.863-878
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    • 2009
  • Unsteady three-dimensional flowfield generated by transverse fuel injection into a supersonic mainstream is simulated with a DES turbulence model. Comparisons are made with experimental results in terms of the temporal eddy position and eddy formation frequency. The vorticity field around the jet exit is also analyzed to understand the formation mechanism of the large eddy structures. Results indicate that the DES model correctly predicts the convection characteristics of the large scale eddies. However, it is also observed that the numerical results slightly over-predict the eddy formation frequency. The large eddy structures are generated as the counter-rotating vortices are detached alternately in the upstream recirculation region.

Detached Eddy Simulation of a Developing Turbulent Flow in a 270° Curved Duct (DES 기법을 이용한 270°곡덕트에서 발달하는 난류 유동의 수치해석)

  • Seo, Jeong-Sik;Shin, Jong-Keun;Choi, Young-Don;Lee, Joo-Cheol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.6
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    • pp.471-478
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    • 2008
  • Detached Eddy Simulation (DES) is performed for developing turbulent flow of the $270^{\circ}$ curved duct at a Reynolds number of 56,690. The curvature ratio on the basis of a centric radius $R_c$ and a duct height H is 3.357. Turbulence models adopted are k-$\omega$ model for Reynolds Average Navier-Stokes (RANS) equation Simulation and Shear Stress Transport (SST) model for DES. DES is used as the hybrid computation technique combined with RANS-SST and Large Eddy Simulation (LES). Predicted results are compared with measured results including the distributions of Reynolds stresses and the flow characteristics on the symmetric plane of curved duct are presented. Judging from the comparison between the predicted and the measured results, the DES approach is applicable to calculate the developing turbulent flow in a $270^{\circ}$ curved duct.

Large Eddy Simulation of Free Motion of Marine Riser using OpenFOAM (오픈폼을 활용한 자유진동하는 라이저 주위 유동의 LES 해석)

  • Jung, Jae-Hwan;Jeong, Kwang-Leol;Gill, Jae-Heung;Jung, Dongho
    • Journal of Ocean Engineering and Technology
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    • v.33 no.5
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    • pp.387-393
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    • 2019
  • In this study, the free motion of a riser due to vortex shedding was numerically simulated with Large Eddy Simulation (LES) and Detached Eddy Simulation (DES) turbulence models. A numerical simulation program was developed by applying the Rhie-Chow interpolation method to the pressure correction of the OpenFOAM standard solver pimpleDyMFoam. To verify the developed program, the vortex shedding around the fixed riser at Re = 3900 was calculated, and the results were compared with the existing experimental and numerical data. Moreover, the vortex-induced vibration of a riser supported by a linear spring was numerically simulated while varying the spring constant. The results are compared with published direct numerical simulation (DNS) results. The present calculation results show that the numerical method is appropriate for simulating the vortex-induced motion of a riser, including lock-in phenomena.

Multiscale finite element method applied to detached-eddy simulation for computational wind engineering

  • Zhang, Yue;Khurram, Rooh A.;Habashi, Wagdi G.
    • Wind and Structures
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    • v.17 no.1
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    • pp.1-19
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    • 2013
  • A multiscale finite element method is applied to the Spalart-Allmaras turbulence model based detached-eddy simulation (DES). The multiscale arises from a decomposition of the scalar field into coarse (resolved) and fine (unresolved) scales. It corrects the lack of stability of the standard Galerkin formulation by modeling the scales that cannot be resolved by a given spatial discretization. The stabilization terms appear naturally and the resulting formulation provides effective stabilization in turbulent computations, where reaction-dominated effects strongly influence near-wall predictions. The multiscale DES is applied in the context of high-Reynolds flow over the Commonwealth Advisory Aeronautical Council (CAARC) standard tall building model, for both uniform and turbulent inflows. Time-averaged pressure coefficients on the exterior walls are compared with experiments and it is demonstrated that DES is able to resolve the turbulent features of the flow and accurately predict the surface pressure distributions under atmospheric boundary layer flows.