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Numerical and experimental study of separated flow in a plane asymmetric diffuser
KTH, Superseded Departments, Mechanics.
KTH, Superseded Departments, Mechanics.
KTH, Superseded Departments, Mechanics.
KTH, Superseded Departments, Mechanics.ORCID iD: 0000-0003-3336-1462
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2004 (English)In: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 25, no 3, 451-460 p.Article in journal (Refereed) Published
Abstract [en]

Computations of the turbulent flow through plane asymmetric diffusers for opening angles from 8degrees to 10degrees have been carried out with the explicit algebraic Reynolds stress model (EARSM) of Wallin and Johansson [J. Fluid Mech. 403 (2000) 89]. It is based on a two-equation platform in the form of a low-Re K - omega formulation, see e.g. Wilcox [Turbulence Modeling for CFD, DCW Industries Inc., 1993]. The flow has also been studied experimentally for the 8.5degrees opening angle using PIV and LDV. The models under-predict the size and magnitude of the recirculation zone. This is, at least partially, attributed to an over-estimation of the wall normal turbulence component in a region close to the diffuser inlet and to the use of damping functions in the near-wall region. By analyzing the balance between the production and dissipation of the turbulence kinetic energy we find that the predicted dissipation is too large. Hence, we can identify a need for improvement of the modeling the transport equation for the turbulence length-scale related quantity.

Place, publisher, year, edition, pages
2004. Vol. 25, no 3, 451-460 p.
Keyword [en]
plane asymmetric diffuser, separated flow, explicit algebraic Reynolds stress model, EARSM, automated code generation
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-6048DOI: 10.1016/j.ijheatfluidflow.2004.02.012ISI: 000222282000014Scopus ID: 2-s2.0-2542557398OAI: oai:DiVA.org:kth-6048DiVA: diva2:10633
Conference
3rd International Symposium on Turbulence and Shear Flow Phenomena (TSFP-3) Sendai, JAPAN, JUN 25-27, 2003
Note
QC 20100923Available from: 2006-08-09 Created: 2006-08-09 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Experimental and computational studies of turbulent separating internal flows
Open this publication in new window or tab >>Experimental and computational studies of turbulent separating internal flows
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The separating turbulent flow in a plane asymmetric diffuser with 8.5 degrees opening angle is investigated experimentally and computationally. The considered flow case is suitable for fundamental studies of separation, separation control and turbulence modelling. The flow case has been studied in a specially designed wind-tunnel under well controlled conditions. The average velocity and fluctuation fields have been mapped out with stereoscopic particle image velocimetry (PIV). Knowledge of all velocity components allows the study of several quantities of interest in turbulence modelling such as the turbulence kinetic energy, the turbulence anisotropy tensor and the turbulence production rate tensor. Pressures are measured through the diffuser. The measured data will form a reference database which can be used for evaluation of turbulence models and other computational investigations. Time-resolved stereoscopic PIV is used in an investigation of turbulence structures in the flow and their temporal evolution. A comparative study is made where the measured turbulence data are used to evaluate an explicit algebraic Reynolds stress turbulence model (EARSM). A discussion regarding the underlying reasons for the discrepancies found between the experimental and the model results is made. A model for investigations of separation suppression by means of vortex generating devices is presented together with results from the model in the plane asymmetric diffuser geometry. A short article on the importance of negative production-rates of turbulent kinetic energy for the reverse flow region in separated flows is presented. A detailed description of the experimental setup and PIV measurement procedures is given in a technical report.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. ix, 185 p.
Series
Trita-MEK, ISSN 0348-467X ; 2006:15
Keyword
Fluid mechanics, turbulence, flow separation, turbulence modelling, asymmetric diffuser, boundary layer, PIV, vortex generator, separation control
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-4071 (URN)91-7178-416-0 (ISBN)
Public defence
2006-09-08, Salongen, Biblioteket KTH, Osquars backe 31, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20100923Available from: 2006-08-09 Created: 2006-08-09 Last updated: 2010-09-23Bibliographically approved

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Amberg, GustavJohansson, Arne V.

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