• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.558-563
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• 2007

Detached Eddy Simulation(DES) is performed for turbulent flow of the $270^{\circ}$ bend at a Reynolds number of 56,690. A Fine grid generation is used near a wall in order to satisfy the wall boundary condition of y+<1. Turbulence models adopted for DES and Reynolds Average Navier Stokes(RANS) simulation are SST(Shear Stress Transfort) model. Solutions for both streamwise and circumferential velocity components are compared with the experimental data by Lee for $270^{\circ}$ bend and by Chang for $180^{\circ}$ bend.

• Journal of computational fluids engineering
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• v.11 no.2 s.33
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• pp.25-31
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• 2006

A two-dimensional backward facing step flow is simulated by using URANS and Detached Eddy Simulations(DES) approaches. Turbulence models adopted for URANS and DES simulations are Spalart-Allmaras(S-A) model and Shear Stress Transport(SST) model. The target flow with ER=1.125, $Re_H=37,500$ is experimentally studied by Driver & Seegmiller. Various versions of DES have been tested in this paper. Results of the simulations are compared with the experimental data available to evaluate the merits and demerits of URANS and several versions of DES. URANS simulation converges to a steady state and hence unsteady characteristics are not featured. DES simulations in general successfully mimic large scale structures and oscillation characteristics of the flow.

• Fire Science and Engineering
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• v.29 no.5
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• pp.42-50
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• 2015

Three simulation approaches for turbulence were applied for the computation of propane dispersion in a simplified real-scale urban area with one building:, Large Eddy Simulation (LES), Detached Eddy Simulation (DES), and Unsteady Reynolds Averaged Navier-Stokes (RANS). The computations were performed using FLUENT 14, and the grid system was made with ICEM-CFD. The propane distribution depended on the prediction performance of the three simulation approaches for the eddy structure around the building. LES and DES showed relatively similar results for the eddy structure and propane distribution, while the RANS prediction of the propane distribution was unrealistic. RANS was found to be inappropriate for computation of the gas dispersion process due to poor prediction performance for the unsteady turbulence. Considering the computational results and cost, DES is believed to be the optimal choice for computation of the gas dispersion in a real-scale space.