On the Suitably of RANS Turbulence Models for Modeling Circular Bluff-Body Configurations

2019 ◽  
Author(s):  
Ricardo Franco ◽  
Cesar Celis ◽  
Luís Fernando Figueira da Silva
Keyword(s):  
Bluff Body ◽  
Turbulence Models ◽  
Rans Turbulence Models

Numerical investigation of methanol bluff-body flame using variants of RANS turbulence models with conditional moment closure model

2019 ◽  
pp. 21-30
Author(s):  
R. N. Roy ◽  
S. Sreedhara
Keyword(s):  
Reynolds Stress ◽  
Bluff Body ◽  
Mixture Fraction ◽  
Turbulence Models ◽  
Moment Closure ◽  
Closure Model ◽  
Conditional Moment ◽  
Conditional Moment Closure ◽  
Rans Turbulence Models ◽  
The Mean

In this article, conditional moment closure model (CMC) along with four variants of RANS turbulence models is used for investigating a methanol bluff-body flame. This work attempts to establish the accuracy of turbulence models in predicting the mixing fields, which results in improved predictions of the mean and variance of mixture fraction. This ensures an accurate probability density function (pdf) of the mixture fraction field which is used to obtain unconditional quantities from the conditional quantities calculated from CMC closure. The flow and mixing field are calculated using ANSYS Fluent software by incorporating four different turbulence models viz. standard k-ε (SKE), modified k-ε (MKE), RNG k-ε and Reynolds stress turbulence models. Flow field simulations have been coupled with an in-house CMC solver to obtain the mean flame structure. Profiles of mixture fraction showed an excellent agreement with the experimental data when Reynolds stress turbulence model was used. The unconditional mean temperature and species mass fraction obtained from the CMC model shows improved predictions when coupled with the Reynolds stress turbulence models. Because of inaccurate mixing field and hence the pdf predicted from SKE, MKE and RNG k-ε models, the unconditional quantities showed significant deviations from the experimental results.

EVALUATING RANS TURBULENCE MODELS TO PREDICT THE AIRFLOW IN A DUCT BEND

2018 ◽  
Author(s):  
Marcos Batistella Lopes ◽  
Viviana Mariani ◽  
katia cordeiro ◽  
Claudine BEGHEIN
Keyword(s):  
Turbulence Models ◽  
Rans Turbulence Models

scholarly journals Prediction of Liner Metal Temperature of an Aeroengine Combustor with Multi-Physics Scale-Resolving CFD

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 901
Author(s):  
Davide Bertini ◽  
Lorenzo Mazzei ◽  
Antonio Andreini
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Turbulence Models ◽  
Metal Temperature ◽  
Lean Burn ◽  
Turbulence Scale ◽  
Ansys Fluent ◽  
Multi Scale ◽  
Assessment Tests ◽  
Rans Turbulence Models

Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS turbulence models provide a reasonable prediction, despite some well-known limitations in reproducing the turbulent mixing in highly unsteady flows. Their affordable cost is ideal in the preliminary design steps, whereas, in the detailed phase of the design process, turbulence scale-resolving methods (such as LES or similar approaches) can be preferred to significantly improve the accuracy. Despite that, in dealing with multi-physics and multi-scale problems, as for Conjugate Heat Transfer (CHT) in presence of radiation, transient approaches are not always affordable and appropriate numerical treatments are necessary to properly account for the huge range of characteristics scales in space and time that occur when turbulence is resolved and heat conduction is simulated contextually. The present work describes an innovative methodology to perform CHT simulations accounting for multi-physics and multi-scale problems. Such methodology, named U-THERM3D, is applied for the metal temperature prediction of an annular aeroengine lean burn combustor. The theoretical formulations of the tool are described, together with its numerical implementation in the commercial CFD code ANSYS Fluent. The proposed approach is based on a time de-synchronization of the involved time dependent physics permitting to significantly speed up the calculation with respect to fully coupled strategy, preserving at the same time the effect of unsteady heat transfer on the final time averaged predicted metal temperature. The results of some preliminary assessment tests of its consistency and accuracy are reported before showing its exploitation on the real combustor. The results are compared against steady-state calculations and experimental data obtained by full annular tests at real scale conditions. The work confirms the importance of high-fidelity CFD approaches for the aerothermal prediction of liner metal temperature.

scholarly journals Assessment of Numerical Methods for Plunging Breaking Wave Predictions

2021 ◽  
Vol 9 (3) ◽  
pp. 264
Author(s):  
Shanti Bhushan ◽  
Oumnia El Fajri ◽  
Graham Hubbard ◽  
Bradley Chambers ◽  
Christopher Kees
Keyword(s):  
Solitary Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Wave Crest ◽  
Breaking Wave ◽  
Rans Turbulence Models ◽  
Run Up ◽  
Better Than

This study evaluates the capability of Navier–Stokes solvers in predicting forward and backward plunging breaking, including assessment of the effect of grid resolution, turbulence model, and VoF, CLSVoF interface models on predictions. For this purpose, 2D simulations are performed for four test cases: dam break, solitary wave run up on a slope, flow over a submerged bump, and solitary wave over a submerged rectangular obstacle. Plunging wave breaking involves high wave crest, plunger formation, and splash up, followed by second plunger, and chaotic water motions. Coarser grids reasonably predict the wave breaking features, but finer grids are required for accurate prediction of the splash up events. However, instabilities are triggered at the air–water interface (primarily for the air flow) on very fine grids, which induces surface peel-off or kinks and roll-up of the plunger tips. Reynolds averaged Navier–Stokes (RANS) turbulence models result in high eddy-viscosity in the air–water region which decays the fluid momentum and adversely affects the predictions. Both VoF and CLSVoF methods predict the large-scale plunging breaking characteristics well; however, they vary in the prediction of the finer details. The CLSVoF solver predicts the splash-up event and secondary plunger better than the VoF solver; however, the latter predicts the plunger shape better than the former for the solitary wave run-up on a slope case.

scholarly journals An integral validation technique of RANS turbulence models

2017 ◽  
Vol 149 ◽  
pp. 150-159 ◽  
Author(s):  
Ian Pond ◽  
Alireza Ebadi ◽  
Yves Dubief ◽  
Christopher M. White
Keyword(s):  
Turbulence Models ◽  
Rans Turbulence Models ◽  
Validation Technique

Numerical Simulation of Sand Erosion Phenomena in Square-Section 90 Degree Bend With Linear/Nonlinear RANS Turbulence Models

2007 ◽  
Author(s):  
Masaya Suzuki ◽  
Kazuaki Inaba ◽  
Makoto Yamamoto
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Turbulence Models ◽  
Solid Particles ◽  
Two Phase ◽  
Streamline Curvature ◽  
Sand Erosion ◽  
Rans Turbulence Models ◽  
Wall Deformation ◽  
Bend Flow

Sand erosion is a phenomenon where solid particles impinging to a wall cause serious mechanical damages to the wall surface. This phenomenon is a typical gas-particle two-phase turbulent flow and a multi-physics problem where the flow field, particle trajectory and wall deformation interact with among others. On the other hand, the sand erosion is a serious problem to install pneumatic conveying systems for handling abrasive materials. Incidentally, the bend erosion is typical target of sand erosion experiments and is useful for verification of numerical simulations. Although, the secondary flow which occurs in such a flow field including streamline curvature cannot be reproduced by the standard k-ε model. To predict this flow field, a more universal model which can estimate anisotropic Reynolds stress is required. In the present study, we simulate sand erosion of 90 degree bend with a square cross-section. We use some linear/nonlinear turbulence models to predict the secondary flow of the bend. Besides, the performance of each model to predict clear/eroded bend flow field is studied.

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