An integral validation technique of 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.

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Assessment of Numerical Methods for Plunging Breaking Wave Predictions

Journal of Marine Science and Engineering ◽

10.3390/jmse9030264 ◽

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.

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Comparison of RANS Turbulence Models in Numerical Prediction of Chevron Nozzle Jet Flows

47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition ◽

10.2514/6.2009-499 ◽

2009 ◽

Cited By ~ 2

Author(s):

Konstantin Kurbatskii

Keyword(s):

Turbulence Models ◽

Numerical Prediction ◽

Jet Flows ◽

Rans Turbulence Models ◽

Chevron Nozzle

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CFD simulation of straight and slightly swirling turbulent free jets using different RANS-turbulence models

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2015.05.048 ◽

2015 ◽

Vol 89 ◽

pp. 1117-1126 ◽

Cited By ~ 32

Author(s):

Martin Miltner ◽

Christian Jordan ◽

Michael Harasek

Keyword(s):

Cfd Simulation ◽

Turbulence Models ◽

Free Jets ◽

Rans Turbulence Models

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

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2007-37030 ◽

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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Investigation of the Flow Structures in Supersonic Free and Impinging Jet Flows

Journal of Fluids Engineering ◽

10.1115/1.4023190 ◽

2013 ◽

Vol 135 (3) ◽

Cited By ~ 18

Author(s):

C. Chin ◽

M. Li ◽

C. Harkin ◽

T. Rochwerger ◽

L. Chan ◽

...

Keyword(s):

High Speed ◽

Numerical Study ◽

Experimental Studies ◽

Turbulence Models ◽

Impinging Jet ◽

Optical Methods ◽

Navier Stokes ◽

Jet Flows ◽

Shock Cell ◽

Rans Turbulence Models

A numerical study of compressible jet flows is carried out using Reynolds averaged Navier–Stokes (RANS) turbulence models such as k-ɛ and k-ω-SST. An experimental investigation is performed concurrently using high-speed optical methods such as Schlieren photography and shadowgraphy. Numerical and experimental studies are carried out for the compressible impinging at various impinging angles and nozzle-to-wall distances. The results from both investigations converge remarkably well and agree with experimental data from the open literature. From the flow visualizations of the velocity fields, the RANS simulations accurately model the shock structures within the core jet region. The first shock cell is found to be constraint due to the interaction with the bow-shock structure for nozzle-to-wall distance less than 1.5 nozzle diameter. The results from the current study show that the RANS models utilized are suitable to simulate compressible free jets and impinging jet flows with varying impinging angles.

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