A Comparison of Detached-Eddy Simulation and Reynolds-Stress Modeling Applied to the Flow over a Backward-Facing Step and an Airfoil at Stall

2010 ◽  
Author(s):  
Axel Probst ◽  
Christoph Wolf ◽  
Rolf Radespiel ◽  
Tobias Knopp ◽  
Dieter Schwamborn ◽  
...  
Keyword(s):  
Reynolds Stress ◽  
Detached Eddy Simulation ◽  
Backward Facing Step ◽  
Stress Modeling ◽  
Eddy Simulation

Comparison of DDES and URANS for Unsteady Tip Leakage Flow in an Axial Compressor Rotor

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Yangwei Liu ◽  
Luyang Zhong ◽  
Lipeng Lu
Keyword(s):  
Reynolds Stress ◽  
Large Scale ◽  
Turbulence Modeling ◽  
Axial Compressor ◽  
Small Time ◽  
Detached Eddy Simulation ◽  
Tip Leakage Flow ◽  
Time Step ◽  
Tip Leakage ◽  
Eddy Simulation

Tip leakage vortex (TLV) has a large impact on compressor performance and should be accurately predicted by computational fluid dynamics (CFD) methods. New approaches of turbulence modeling, such as delayed detached eddy simulation (DDES), have been proposed, the computational resources of which can be reduced much more than for large eddy simulation (LES). In this paper, the numerical simulations of the rotor in a low-speed large-scale axial compressor based on DDES and unsteady Reynolds-averaged Navier–Stokes (URANS) are performed, thus improving our understanding of the TLV dynamic mechanisms and discrepancy of these two methods. We compared the influence of different time steps in the URANS simulation. The widely used large time-step makes the unsteadiness extremely weak. The small time-step shows a better result close to DDES. The time-step scale is related to the URANS unsteadiness and should be carefully selected. In the time-averaged flow, the TLV in DDES dissipates faster, which has a more similar structure to the experiment. Then, the time-averaged and instantaneous results are compared to divide the TLV into three parts. URANS cannot give the loss of stability and evolution details of TLV. The fluctuation velocity spectra show that the amplitude of high frequencies becomes obvious downstream from the TLV, where it becomes unstable. Last, the anisotropy of the Reynolds stress of these two methods is analyzed through the Lumley triangle to see the distinction between the methods and obtain the Reynolds stress. The results indicate that the TLV latter part in DDES is anisotropic, while in URANS it is isotropic.

scholarly journals High-order detached-eddy simulation method based on a Reynolds-stress background model

2017 ◽  
Vol 66 (18) ◽  
pp. 184701
Author(s):  
Wang Sheng-Ye ◽  
Wang Guang-Xue ◽  
Dong Yi-Dao ◽  
Deng Xiao-Gang
Keyword(s):  
Reynolds Stress ◽  
Simulation Method ◽  
High Order ◽  
Background Model ◽  
Detached Eddy Simulation ◽  
Eddy Simulation

Numerical Investigation of Compound Angle Effusion Cooling Using Differential Reynolds Stress Model and Zonal Detached Eddy Simulation Approaches

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
G. Arroyo-Callejo ◽  
E. Laroche ◽  
P. Millan ◽  
F. Leglaye ◽  
F. Chedevergne
Keyword(s):  
Reynolds Stress ◽  
Flow Behavior ◽  
Reynolds Stress Model ◽  
Formation Mechanisms ◽  
Stress Model ◽  
Detached Eddy Simulation ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Depth Analysis

Effusion cooling is one of the most effective and widespread techniques to prevent combustor liner from being damaged. However, most recent developments in combustion techniques, resulting from increasingly stricter air pollution regulations, have highlighted the necessity of reducing the amount of air available for effusion cooling while keeping an adequate level of protection. Adoption of compound angles in effusion cooling is increasingly recognized by jet engine manufacturers as a powerful solution to meet new combustor requirements. Therefore, understanding the flow behavior and developing methods able to provide accurate estimates of wall temperatures is of a major importance. This study assesses the capability of a high-level Reynolds-averaged Navier–Stokes (RANS) method, differential Reynolds stress model (DRSM), in conjunction with a generalized gradient diffusion hypothesis (GGDH), and of a hybrid RANS–large eddy simulations (LES) method, zonal detached eddy simulation (ZDES), to predict overall film effectiveness. Both approaches are compared with the experimental data from Zhang et al. (2009, “Cooling Effectiveness of Effusion Walls With Deflection Hole Angles Measured by Infrared Imaging,” Appl. Therm. Eng., 29(5), pp. 966–972) and with a classical well-known RANS model (k–ω shear-stress transport (SST) model). Despite the fact that some discrepancies are found, both approaches have proved suitable and reliable for predicting wall temperatures (relative errors of about 5%). Moreover, a new method to deal with ZDES length scales for unstructured grids is proposed. ZDES applicability and its general advantages and drawbacks are also discussed. Finally, an in-depth analysis of the film structure is carried out on the basis of the ZDES simulations. The principal structures are identified (an asymmetric main vortex (AMV) and a counter rotating vortex pair, CRVP), and the film formation mechanisms are presented. Significant spanwise-homogeneous distributions of surface overall film cooling effectiveness are observed.

A Periodically Perturbed Backward-Facing Step Flow by Means of LES, DES and T-RANS: An Example of Flow Separation Control

2005 ◽  
Vol 127 (5) ◽  
pp. 879-887 ◽  
Author(s):  
S. Šarić ◽  
S. Jakirlić ◽  
C. Tropea
Keyword(s):  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Reattachment Length ◽  
Backward Facing Step ◽  
Inlet Channel ◽  
Flow Separation Control ◽  
Eddy Simulation ◽  
Sst Model ◽  
Perturbation Frequency ◽  
Zero Net Mass Flux

Turbulent flow over a backward-facing step, perturbed periodically by alternative blowing∕suction through a thin slit (0.05H width) situated at the step edge, was studied computationally using (LES) large eddy simulation, (DES) detached eddy simulation, and (T-RANS) transient Reynolds-averaged Navier–Stokes techniques. The flow configuration considered (ReH=UcH∕ν=3700) has been investigated experimentally by Yoshioka et al. (12). The periodic blowing∕suction with zero net mass flux is governed by a sinusoidal law: ve=0.3Ucsin(2πfet), Uc being the centerline velocity in the inlet channel. Perturbation frequencies fe corresponding to the Strouhal numbers St=0.08, 0.19, and 0.30 were investigated (St=feH∕Uc). The experimental observation that the perturbation frequency St=0.19 represents the most effective case, that is the case with the minimum reattachment length, was confirmed by all computational methods. However, the closest agreement with experiment (the reattachment length reduction of 28.3% compared to the unperturbed case) was obtained with LES (24.5%) and DES (35%), whereas the T-RANS computations showed a weaker sensitivity to the perturbation: 5.9% when using the Spalart–Allmaras model and 12.9% using the k-ω SST model.

A New Hybrid RANS/LES Modeling Methodology for CFD Applications

2011 ◽  
Author(s):  
Mohammad F. Alam ◽  
D. Keith Walters ◽  
David S. Thompson
Keyword(s):  
Turbulence Models ◽  
Detached Eddy Simulation ◽  
Backward Facing Step ◽  
Mean Velocity ◽  
New Model ◽  
Rans Model ◽  
Eddy Simulation ◽  
Modeling Methodology ◽  
Sst Model ◽  
Les Model

The primary weakness of current hybrid RANS/LES (HRL) models lies in the treatment of the “transition zone,” where the value and the physical interpretation of the eddy viscosity changes from LES to RANS, or vice versa. In order to address this problem, the initial version of a new HRL modeling methodology has been developed that incorporates two separate turbulent stress parameters (one from the LES model and the other from the RANS model). In this paper, the viability of the new model is demonstrated by predictions of the flow over a backward facing step, which is one of the canonical test cases used for the validation of turbulence models. The simulation results of backward facing step flow at ReH = 37,000 provided by Menter’s Shear Stress Transport (SST) model, a new version of Detached Eddy Simulation (DES) i.e. delayed DES model, and the new model are compared with experiments. Mesh sensitivity of the models is also studied employing two different types of mesh, in order to test the wide applicability of the HRL models in various realistic flow simulations. Pressure and skin friction distributions and mean velocity profiles obtained with the new HRL model show improved agreement with the experimental measurements versus DES, and less sensitivity to the mesh details. Turbulent kinetic energy profiles of both the new model and the RANS model show qualitatively good agreement with experiments.

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