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Simulations of turbulent flow in a plane asymmetric diffuser
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control.ORCID iD: 0000-0001-9627-5903
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control.ORCID iD: 0000-0001-7864-3071
2007 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 79, no 3, 275-306 p.Article in journal (Refereed) Published
Abstract [en]

Large-eddy simulations (LES) of a planar, asymmetric diffuser flow have been performed. The diverging angle of the inclined wall of the diffuser is chosen as 8.5 degrees, a case for which recent experimental data are available. Reasonable agreement between the LES and the experiments is obtained. The numerical method is further validated for diffuser flow with the diffuser wall inclined at a diverging angle of 10 degrees, which has served as a test case for a number of experimental as well as numerical studies in the literature (LES, RANS). For the present results, the subgrid-scale stresses have been closed using the dynamic Smagorinsky model. A resolution study has been performed, highlighting the disparity of the relevant temporal and spatial scales and thus the sensitivity of the simulation results to the specific numerical grids used. The effect of different Reynolds numbers of the inflowing, fully turbulent channel flow has been studied, in particular, Re-b = 4,500, Re-b = 9,000 and Re-b = 20,000 with Re-b being the Reynolds number based on the bulk velocity and channel half width. The results consistently show that by increasing the Reynolds number a clear trend towards a larger separated region is evident; at least for the studied, comparably low Reynolds-number regime. It is further shown that the small separated region occurring at the diffuser throat shows the opposite behaviour as the main separation region, i.e. the flow is separating less with higher Re-b . Moreover, the influence of the Reynolds number on the internal layer occurring at the non-inclined wall described in a recent study has also been assessed. It can be concluded that this region close to the upper, straight wall, is more distinct for larger Re-b . Additionally, the influence of temporal correlations arising from the commonly used periodic turbulent channel flow as inflow condition (similar to a precursor simulation) for the diffuser is assessed.

Place, publisher, year, edition, pages
2007. Vol. 79, no 3, 275-306 p.
Keyword [en]
turbulent separation, diffuser flow, large-Eddy simulation, dynamic Smagorinsky model, large-eddy simulation, direct numerical-simulation, boundary-layer, separated flow, channel, models
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-16949DOI: 10.1007/s10494-007-9091-5ISI: 000249405300005Scopus ID: 2-s2.0-34548592017OAI: oai:DiVA.org:kth-16949DiVA: diva2:334992
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-08-30Bibliographically approved
In thesis
1. Numerical Studies of Turbulent and Separeted Flows
Open this publication in new window or tab >>Numerical Studies of Turbulent and Separeted Flows
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 36 p.
Series
Trita-MEK, ISSN 0348-467X ; 2006:12
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-4044 (URN)
Public defence
2006-06-16, Sal F3, Lindstedtsvägen 26, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20100830Available from: 2006-06-08 Created: 2006-06-08 Last updated: 2010-08-30Bibliographically approved

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Schlatter, PhilippHenningson, Dan S.

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