Explicit algebraic Reynolds stress and non-linear eddy-viscosity models

Design and optimization of an efficient internal air system of a gas turbine requires thorough understanding of the flow and heat transfer in rotating disc cavities. The present study is devoted to numerical modelling of flow and heat transfer in a cylindrical cavity with radial inflow and comparison with the available experimental data. The simulations are carried out with axi-symmetric and 3-D sector models for various inlet swirl and rotational Reynolds numbers upto 2.1×106. The pressure coefficients and Nusselt numbers are compared with the available experimental data and integral method solutions. Two popular eddy viscosity models, the Spalart-Allmaras and the k-ε, and a Reynolds stress model have been used. For cases with particularly strong vortex behaviour the eddy viscosity models show some shortcomings with the Spalart-Allmaras model giving slightly better results than the k-ε model. Use of the Reynolds stress model improved the agreement with measurements for such cases. The integral method results are also found to agree well with the measurements.

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Performance Evaluation of a Non-Linear Explicit Algebraic Reynolds Stress Model for Surface Mounted Obstacles

Volume 3: Computational Fluid Dynamics; Micro and Nano Fluid Dynamics ◽

10.1115/fedsm2020-20304 ◽

2020 ◽

Author(s):

Benjamin H. Taylor ◽

Tausif Jamal ◽

D. Keith Walters

Keyword(s):

Reynolds Stress ◽

Eddy Viscosity ◽

Numerical Data ◽

Reynolds Stress Model ◽

Stress Model ◽

Rans Model ◽

Non Linear ◽

Additional Strain ◽

Dynamic Hybrid ◽

Algebraic Reynolds Stress Model

Abstract The presence of complex vortical structures, unsteady wakes, separated shear layers, and streamline curvature pose considerable challenges for traditional linear Eddy-Viscosity (LEV) models. Since Non-Linear Eddy Viscosity Models (NEV) models contain additional strain-rate and vorticity relationships, they can provide a better description for flows with Reynolds stress anisotropy and can be considered to be suitable alternatives to traditional EVMs in some cases. In this study, performance of a Non-Linear Explicit Algebraic Reynolds Stress Model (NEARSM) to accurately resolve flow over a surface mounted cube and a 3D axisymmetric hill is evaluated against existing experimental and numerical studies. Numerical simulations were performed using the SST k-ω RANS model, SST k-ω-NEARSM, SST-Multiscale LES model, and two variants of the Dynamic Hybrid RANS-LES (DHRL) model that include the SST k-ω and the SST k-ω-NEARSM as the RANS models. Results indicate that the SST k-ω RANS model fails to accurately predict the flowfield in the separated wake region and although the SST-NEARSM and SST-Multiscale LES models provide an improved description of the flow, they suffer from incorrect RANS-LES transition caused by Modeled Stress Depletion (MSD) and sensitivity to changes in grid resolution. The SST-DHRL and the SST-NEARSM-DHRL variants provide the best agreement to experimental and numerical data.

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Computational prediction of flow around highly loaded compressor-cascade blades with non-linear eddy-viscosity models

International Journal of Heat and Fluid Flow ◽

10.1016/s0142-727x(98)10001-2 ◽

1998 ◽

Vol 19 (4) ◽

pp. 307-319 ◽

Cited By ~ 24

Author(s):

W.L. Chen ◽

F.S. Lien ◽

M.A. Leschziner

Keyword(s):

Eddy Viscosity ◽

Computational Prediction ◽

Compressor Cascade ◽

Viscosity Models ◽

Non Linear ◽

Highly Loaded

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Applications of EARSM Turbulence Models to Internal Flows

Volume 8: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2012-68886 ◽

2012 ◽

Cited By ~ 2

Author(s):

O. Z. Mehdizadeh ◽

L. Temmerman ◽

B. Tartinville ◽

Ch. Hirsch

Keyword(s):

Reynolds Stress ◽

High Performance ◽

Eddy Viscosity ◽

Computational Cost ◽

Turbulence Models ◽

Industrial Applications ◽

Mean Flow ◽

Viscosity Models ◽

Stress Models ◽

Corner Flows

Turbulence modeling remains an active CFD development front for turbomachinery as well as for general industrial applications. While DNS and even LES still seem out of reach within the typical industrial design cycle due to their high computational cost, RANS-based models remain the workhorse of CFD. Currently, the most widely used models are Linear Eddy-Viscosity Models (LEVM), despite their known limitations for certain flow complexities. Therefore, extending the reliability of eddy-viscosity models to more complex flows without significantly increasing the computational cost can immediately contribute to more reliable CFD results for wider range of applications. This, in turn, can further reduce the need for costly tests and consequently can reduce the product development cost. A promising approach to achieve this goal is using Explicit Algebraic Reynolds Stress Models (EARSM), obtained through a simplification of the full Differential Reynolds Stress Models (DRSM), and can be perceived as an extension of LEVMs by including the non-linear relation between the turbulence stress tensor, the mean-flow gradient and the turbulence scales. These models are thus less demanding than DRSM, yet capable of capturing more complex turbulence features, compared to LEVM, such as anisotropy in the normal stresses. This may be particularly important in corner flows, for instance, in the hub-blade regions or in diffusers. This work explores the application of EARSM models to a double diffuser and a high-performance centrifugal compressor stage (HPCC). The results are compared to available experimental data [1,2] showing the importance of including the anisotropy of turbulence in the model, particularly in presence of turbulent corner flows in a diffuser. Furthermore, the EARSM results are also compared to results from the commonly used SST turbulence model. The CFD comparison includes details of the flow structure in the diffuser, where the most noticeable impact from the use of EARSM turbulence models is expected.

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