Some Swirling-flow Challenges for Turbulent CFD

Craft, Tim; Iacovides, Hector; Launder, B. E.; Zacharos, Athanasios

doi:10.1007/s10494-008-9156-0

Cited by 23 publications

(17 citation statements)

References 20 publications

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“…It is now well known RANS based eddy viscosity models, such as the k-ǫ model perform very poorly in strongly swirling flows. Second moment closures fare somewhat better, see for example Craft et al (2008), although even these appear to be incapable of accurately reproducing the unsteady large scale structures that appear in strongly swirling confined flows. Both LES and unsteady RANS were applied in Dunham et al (2009) to model the flow in a single swirl stream fuel injector where the capability of LES to reproduce flow characteristics was shown to be in excellent agreement with measurements.…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulations of isothermal confined swirling flow in an industrial gas-turbine

Bulat

Jones

Navarro‐Martinez

2015

International Journal of Heat and Fluid Flow

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The paper describes the results of a computational study of the strongly swirling isothermal flow in the combustion chamber of an industrial gas turbine. The flow field characteristics are computed using Large Eddy Simulation in conjunction with a dynamic version of the Smagorinsky model for the sub-grid-scale stresses.Grid refinement studies demonstrate that the results are essentially grid independent. The LES results are compared with an extensive set of measurements and the agreement with these is overall good. The method is shown to be capable of reproducing the observed Precessing Vortex and Central Vortex Cores and the profiles of mean and rms velocities are found to be captured to a good accuracy. The overall flow structure is shown to be virtually independent of Reynolds number.

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Section: Introductionmentioning

confidence: 99%

Large eddy simulations of isothermal confined swirling flow in an industrial gas-turbine

Bulat

Jones

Navarro‐Martinez

2015

International Journal of Heat and Fluid Flow

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“…There is no effect of inflow condition (turbulence level) and the flow can also involve multiple regimes such as laminar, transitional, fully turbulent and relaminarization. A renewed interest for these flows was born from the appearance of precessing large scale vortical structures embedded in the turbulent regime, first observed experimentally by [5] and confirmed numerically by the URANS computations of [4].…”

Section: Introductionmentioning

confidence: 99%

High-order Large Eddy Simulations of Confined Rotor-Stator Flows

Viazzo

Poncet

Serre

et al. 2011

Flow Turbulence Combust

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In many engineering and industrial applications, the investigation of rotating turbulent flow is of great interest. In rotor-stator cavities, the centrifugal and Coriolis forces have a strong influence on the turbulence by producing a secondary flow in the meridian plane composed of two thin boundary layers along the disks separated by a non-viscous geostrophic core. Most numerical simulations have been performed using RANS and URANS modelling, and very few investigations have been performed using LES. This paper reports on quantitative comparisons of two high-order LES methods to predict a turbulent rotor-stator flow at the rotational Reynolds number Re=400000. The classical dynamic Smagorinsky model for the subgrid-scale stress (Germano et al., Phys Fluids A 3(7):1760-1765, 1991) is compared to a spectral vanishing viscosity technique (S\'everac & Serre, J Comp Phys 226(2):1234-1255, 2007). Numerical results include both instantaneous data and postprocessed statistics. The results show that both LES methods are able to accurately describe the unsteady flow structures and to satisfactorily predict mean velocities as well as Reynolds stress tensor components. A slight advantage is given to the spectral SVV approach in terms of accuracy and CPU cost. The strong improvements obtained in the present results with respect to RANS results confirm that LES is the appropriate level of modelling for flows in which fully turbulent and transition regimes are involved

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“…Craft et al [15] performed URANS simulations of the above mentioned experiments. The simulation of the disk cavity was done using a two-equation turbulence model, and similar to the results presented in this report, Craft's simulations did not reach stability even after 70 revolutions.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the sealing effectiveness (g c ) is not predicted accurately. Craft et al [15] showed in his simulation of disk cavities using a two-equation turbulence model that the flow does not reach steady state even after 70 revolutions. The present work simulates the experimental rig geometry of Balasubramanian et al [16] in a 360 unsteady CFD model, runs the simulation under rig conditions, and then compares the CFD predictions of pressure, velocity, and concentration-based cavity effectiveness (g c ) with the experimental data of [16].…”

Section: Introductionmentioning

confidence: 99%

Unsteady 360 Computational Fluid Dynamics Validation of a Turbine Stage Mainstream/Disk Cavity Interaction

Mirzamoghadam

Kanjiyani

Riahi

et al. 2014

Journal of Turbomachinery

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The amount of cooling air assigned to seal high pressure turbine (HPT) rim cavities is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disk or cover plate life. Excessive purge air, on the other hand, adversely affects performance. Experiments on a rotating turbine stage rig which included a rotor-stator forward disk cavity were performed at Arizona State University (ASU). The turbine rig has 22 vanes and 28 blades, while the cavity is composed of a single-tooth lab seal and a rim platform overlap seal. Time-averaged static pressures were measured in the gas path and the cavity, while mainstream gas ingestion into the cavity was determined by measuring the concentration distribution of tracer gas (carbon dioxide) under a range of purge flows from 0.435% (C w ¼ 1540) to 1.74% (C w ¼ 6161). Additionally, particle image velocimetry (PIV) was used to measure fluid velocity inside the cavity between the lab seal and the rim seal. The data from the experiments were compared to time-dependent computational fluid dynamics (CFD) simulations using FLUENT CFD software. The CFD simulations brought to light the unsteadiness present in the flow during the experiment which the slower response data did not fully capture. An unsteady Reynolds averaged Navier-Stokes (RANS), 360-deg CFD model of the complete turbine stage was employed in order to increase the understanding of the swirl physics which dominate cavity flows and better predict rim seal ingestion. Although the rotor-stator cavity is geometrically axisymmetric, it was found that the interaction between swirling flows in the cavity and swirling flows in the gas path create nonperiodic/time-dependent unstable flow patterns which at the present are not accurately modeled by a 360 deg full stage unsteady analysis. At low purge flow conditions, the vortices that form inside the cavities are greatly influenced by mainstream ingestion. Conversely at high purge flow conditions the vortices are influenced by the purge flow, therefore ingestion is minimized. The paper also discusses details of meshing, convergence of time-dependent CFD simulations, and recommendations for future simulations in a rotor-stator disk cavity such as assessing the observed unsteadiness in the frequency domain in order to identify any critical frequencies driving the system.

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Some Swirling-flow Challenges for Turbulent CFD

Cited by 23 publications

References 20 publications

Large eddy simulations of isothermal confined swirling flow in an industrial gas-turbine

Large eddy simulations of isothermal confined swirling flow in an industrial gas-turbine

High-order Large Eddy Simulations of Confined Rotor-Stator Flows

Unsteady 360 Computational Fluid Dynamics Validation of a Turbine Stage Mainstream/Disk Cavity Interaction

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