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Taking large-eddy simulation of wall-bounded flows to higher Reynolds numbers by use of anisotropy-resolving subgrid models
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0002-9819-2906
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0002-2711-4687
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0001-8692-0956
2017 (English)In: Physical Review Fluids, E-ISSN 2469-990X, Vol. 2, article id 034601Article in journal (Refereed) Published
Abstract [en]

Properly resolved large-eddy simulations of wall-bounded high Reynolds number flows using standard subgrid-scale (SGS) models requires high spatial and temporal resolution. We have shown that a more elaborate SGS model taking into account the SGS Reynolds stress anisotropies can relax the requirement for the number of grid points by at least an order of magnitude for the same accuracy. This was shown by applying the recently developed explicit algebraic subgrid-scale model (EAM) to fully developed high Reynolds number channel flows with friction Reynolds numbers of 550, 2000, and 5200. The near-wall region is fully resolved, i.e., no explicit wall modeling or wall functions are applied. A dynamic procedure adjusts the model at the wall for both low and high Reynolds numbers. The resolution is reduced, from the typically recommended 50 and 15 wall units in the stream-and spanwise directions respectively, by up to a factor of 5 in each direction. It was shown by comparison with direct numerical simulations that the EAM is much less sensitive to reduced resolution than the dynamic Smagorinsky model. Skin friction coefficients, mean flow profiles, and Reynolds stresses are better predicted by the EAM for a given resolution. Even the notorious overprediction of the streamwise fluctuation intensity typically seen in poorly resolved LES is significantly reduced whenEAMis used on coarse grids. The improved prediction is due to the capability of the EAM to capture the SGS anisotropy, which becomes significant close to the wall.

Place, publisher, year, edition, pages
American Physical Society, 2017. Vol. 2, article id 034601
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:kth:diva-220931DOI: 10.1103/PhysRevFluids.2.034601ISI: 000396070400001Scopus ID: 2-s2.0-85028541529OAI: oai:DiVA.org:kth-220931DiVA, id: diva2:1172386
Note

QC 20180110

Available from: 2018-01-09 Created: 2018-01-09 Last updated: 2024-03-18Bibliographically approved
In thesis
1. Numerical and modelling aspects of large-eddy and hybrid simulations of turbulent flows
Open this publication in new window or tab >>Numerical and modelling aspects of large-eddy and hybrid simulations of turbulent flows
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this study, the explicit algebraic sub-grid scale (SGS) model (EAM) has been extensively validated in wall-resolved large-eddy simulations (LES) of wall-bounded turbulent flows at different Reynolds numbers and a wide range of resolutions. Compared to eddy-viscosity based models, the formulation of the EAM is more consistent with the physics and allows to accurately capture SGS anisotropy,which is relevant especially close to walls.The present work aims to extend the validation of the EAM to larger Reynolds numbers using codes with different orders of numerical accuracy.The first simulations, performed by using a pseudo-spectral code, show that the use of the EAM, compared to the dynamic Smagorinsky model (DSM), leads to significant improvements in the prediction of the first-and second order statistics of turbulent channel flow.These improvements are observed from relatively low to  reasonably high Reynolds numbers and with coarse grids.The evaluation of the EAM was continued by implementing and testing of the EAM in the general-purpose finite-volume code OpenFOAM.Several tests of LES of turbulent channel flow have shown thatthe use of the Rhie and Chow (R&C) interpolation in OpenFOAM induces significant numerical dissipation.A new custom-built solver has been utilized in order to minimize the dissipation without generating significant adverse effects. The use of the EAM, together with the new solver, gives a substantially improved prediction of the mean velocity profiles as compared to predictions using the DSM, resulting in roughly 50% reduction in the grid point requirements to achieve a given degree of accuracy. In periodic hill flow, LES with the EAM agreed reasonably well with the reference dataat different bulk Reynolds numbers and reduced the misprediction of the first- and second order statistics observed in LES with DSM.The reduction of the R&C filter dissipation was also shown to be beneficial for the prediction of the mean quantities. An analysis of the skin friction along the lower wall reveals spanwise-elongated, almost axi-symmetric vortical structures generated by the Kelvin-Helmholtz instability. The structures introduced a significant amount of anisotropy.The last part of the study involved the development of a novel hybrid RANS-LES model where explicit algebraic Reynolds stress modelling is applied in both RANS and LES regions.Validations have been conducted on turbulent channel and periodic hill flows at different Reynolds numbers.The explicit algebraic Reynolds stress model for improved-delayed-detached-eddy simulation (EARSM-IDDES) gives reasonable predictions of the mean quantities and Reynolds stresses in both the geometries considered.The use of EARSM-IDDES, compared to the k-omega SST-IDDES model, improves the estimation of the quantities close to the wall.The present work has proven that the use of EAM in wall-resolved LES of wall-bounded flows in simple and complex geometries leads to a substantial reduction of  computational requirements both in high-accuracy and general-purpose codes, compared to the use of eddy-viscosity models.In hybrid simulations the EARSM-IDDES shows a clear potential in capturing the physics of wall-bounded flows.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 60
Series
TRITA-SCI-FOU ; 2019:48
Keywords
turbulence, wall-bounded flows, large-eddy simulation, SGS modelling, OpenFOAM, hybrid RANS-LES
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-264025 (URN)978-91-7873-369-9 (ISBN)
Public defence
2019-12-19, F3, Lindstedtsvägen 26, Stockholm, 10:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2014- 5700Vinnova, 2017-04887
Note

QC 20191122

Available from: 2019-11-22 Created: 2019-11-20 Last updated: 2022-06-26Bibliographically approved

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Montecchia, MatteoBrethouwer, GertJohansson, Arne V.Wallin, Stefan

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