Studying the Channel Confluence Hydraulics Using Eddy Viscosity Models and Reynolds Stress Model

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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On the Application of the Full Reynolds Stress Model for Unsteady CFD in Hydraulic Turbomachines

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

10.1115/fedsm2020-20398 ◽

2020 ◽

Author(s):

Ernesto Casartelli ◽

Luca Mangani ◽

David Roos ◽

Armando Del Rio

Keyword(s):

Reynolds Stress ◽

Eddy Viscosity ◽

Reynolds Stress Model ◽

Moment Closure ◽

Flow Structures ◽

Stress Model ◽

Cfd Simulations ◽

Viscosity Models ◽

Hydraulic Machines ◽

Fully Coupled

Abstract The computation of the characteristic of hydraulic machines, both in pump and turbine mode, needs, when performed over a wide operating range, to take into account turbulence anisotropy. This because highly separated flows largely deviate from isotropic turbulence structures as assumed in RANS eddy viscosity models with the Boussinesq approximation. In this paper CFD computations were performed with anisotropic turbulence models in order to capture the characteristic and investigate flow structures phenomena. Experimental results are compared against the CFD simulations in order to validate the results. Specific occurring phenomena are highlighted and more complex flow structures are evident compared to those computed with standard eddy viscosity models. A in-house pressure based coupled solver was used for the CFD simulations. The code is a finite volume polyhedral CFD solver implemented in a C++ framework with the possibility to implement implicit and coupled algorithms. Second moment closure turbulence model have been successfully implemented with a standard and novel fully coupled algorithm. In the paper the advantage of the novel algorithm is presented for industrial applications. The fully coupled approach for the Reynolds Stress model allows stable simulations of transient and steady state hydraulic machines at any operating point, opening also new opportunities in obtaining high accurate results for anisotropic turbulent flows without the usage of hybrid LES/RANS models and without the model limitation of standard eddy viscosity models.

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Rotating Flow and Heat Transfer in Cylindrical Cavities With Radial Inflow

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4007826 ◽

2013 ◽

Vol 135 (3) ◽

Cited By ~ 9

Author(s):

B. G. Vinod Kumar ◽

John W. Chew ◽

Nicholas J. Hills

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Reynolds Stress ◽

Integral Method ◽

Eddy Viscosity ◽

Reynolds Stress Model ◽

Stress Model ◽

Rotating Disc ◽

Flow And Heat Transfer ◽

Viscosity Models

The design and optimization of an efficient internal air system of a gas turbine requires a thorough understanding of the flow and heat transfer in rotating disc cavities. The present study is devoted to the numerical modeling of flow and heat transfer in a cylindrical cavity with radial inflow and a comparison with the available experimental data. The simulations are carried out with axisymmetric and 3-D sector models for various inlet swirl and rotational Reynolds numbers up to 1.2 × 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-ɛ, and a Reynolds stress model have been used. For cases with particularly strong vortex behavior the eddy viscosity models show some shortcomings, with the Spalart–Allmaras model giving slightly better results than the k-ɛ 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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Structural Parameters and Prediction of Adverse Pressure Gradient Turbulent Flows: An Improved k-ε Model

Journal of Fluids Engineering ◽

10.1115/1.2817279 ◽

1995 ◽

Vol 117 (3) ◽

pp. 424-432 ◽

Cited By ~ 1

Author(s):

G. Chukkapalli ◽

O¨. F. Turan

Keyword(s):

Pressure Gradient ◽

Turbulent Flows ◽

Reynolds Stress ◽

Eddy Viscosity ◽

Structural Parameters ◽

Adverse Pressure Gradient ◽

Reynolds Stress Model ◽

Model Representation ◽

Stress Model ◽

Kinetic Diffusion

A modified k-ε model is proposed to predict complex, adverse pressure gradient, turbulent diffuser flows. The need for an eddy viscosity is eliminated by using three structural parameters. A fuller treatment of the rate of kinetic diffusion terms is incorporated with a Reynolds stress model representation. A thorough evaluation is given of the three structural parameters in three decreasing and one increasing adverse pressure gradient diffuser flows leading to a three-layer representation. The results indicate the need for better modeling of the ε-equation.

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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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Turbulence Modeling in a Model Combustor

Volume 2: Turbo Expo 2005 ◽

10.1115/gt2005-68403 ◽

2005 ◽

Cited By ~ 1

Author(s):

Lei-Yong Jiang ◽

Ian Campbell

Keyword(s):

Reynolds Stress ◽

Eddy Viscosity ◽

Turbulence Modeling ◽

Turbulence Models ◽

Reynolds Stress Model ◽

Moment Closure ◽

Superior Performance ◽

Combustion Model ◽

Discrete Ordinates ◽

Viscosity Models

The flow field of a propane-air diffusion flame combustor with interior and exterior conjugate heat transfers was numerically investigated. Solutions obtained from four turbulence models together with a laminar flamelet combustion model, discrete ordinates radiation model and enhanced wall treatment are presented and discussed. The numerical results are compared, in detail, with a comprehensive database obtained from a series of experimental measurements. It is found that the Reynolds stress model (RSM), a second moment closure, illustrates superior performance over three popular two-equation eddy-viscosity models. Although the main flow features are captured by all four turbulence models, only the RSM is able to successfully predict the lengths of both recirculation zones and the turbulence kinetic energy distribution in the combustor chamber. In addition, it provides fairly good predictions for all Reynolds stress components, except for the circumferential normal stress at downstream sections. However, the superiority of the RSM is not so obvious for the temperature and species predictions in comparison with eddy-viscosity models, except for the standard k-ε model. This suggests that coupling between the RSM and combustion models needs to be further improved in order to enhance its applications in practical combustion systems.

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Second-Moment Closure Model for IC Engine Flow Simulation Using Kiva Code1

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.483213 ◽

1999 ◽

Vol 122 (2) ◽

pp. 355-363 ◽

Cited By ~ 10

Author(s):

S. L. Yang ◽

B. D. Peschke ◽

K. Hanjalic

Keyword(s):

Reynolds Stress ◽

Eddy Viscosity ◽

Flow Simulation ◽

Reynolds Stress Model ◽

Tensor Component ◽

Moment Closure ◽

Stress Model ◽

Closure Model ◽

Ic Engine ◽

Second Moment

The flow and turbulence in an IC engine cylinder were studied using the SSG variant of the Reynolds stress turbulence closure model. In-cylinder turbulence is characterized by strong turbulence anisotropy and flow rotation, which aid in air-fuel mixing. It is argued that solving the differential transport equations for each turbulent stress tensor component, as implied by second-moment closures, can better reproduce stress anisotropy and effects of rotation, than with eddy-viscosity models. Therefore, a Reynolds stress model that can meet the demands of in-cylinder flows was incorporated into an engine flow solver. The solver and SSG turbulence model were first successfully tested with two different validation cases. Finally, simulations were applied to IC-engine like geometries. The results showed that the Reynolds stress model predicted additional flow structures and yielded less diffusive profiles than those predicted by an eddy-viscosity model. [S0742-4795(00)00101-0]

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