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Numerical and theoretical investigation of pulsatile turbulent channel flows
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0002-7203-0503
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0003-4103-0129
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0002-5913-5431
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The turbulent channel flow subjected to imposed harmonic oscillations is studied by theo- retical models and direct numerical simulations (DNS). A linear model proposed earlier by the present authors for the coherent perturbation Reynolds shear stress is reviewed and discussed in depth. The model includes the non-equilibrium effects during the response of the Reynolds stress to the imposed periodic shear straining, where a phase lag exists between the stress and the strain. To validate the model, the DNS results are compared with the perturbation velocity and Reynolds shear stress computed from the model. The performance of the model is good in the frequency range where quasi-static assumptions are invalid, and the viscoelastic characteris- tics of the turbulent eddies implied by the model is supported by the DNS. Attempts to improve the model are also made by incorporating in the model the DNS data. In addition, the onset of the nonlinear effects during the production of the perturbation Reynolds stresses are discussed based on the DNS data, new physical features observed from the DNS are reported. 

National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-168030OAI: oai:DiVA.org:kth-168030DiVA: diva2:814008
Funder
Swedish Research Council, SDA 26211
Note

QS 2015

Available from: 2015-05-25 Created: 2015-05-25 Last updated: 2015-05-26Bibliographically approved
In thesis
1. Theoretical and numerical studies of sound propagation in low-Mach-number duct flows
Open this publication in new window or tab >>Theoretical and numerical studies of sound propagation in low-Mach-number duct flows
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

When sound waves propagate in a duct in the presence of turbulent flow, turbulent mixing can cause attenuation of the sound waves extra to that caused by the viscothermal effects. Experiments show that compared to the viscothermal effects, this turbulent absorption becomes the dominant contribution to the sound attenuation at sufficiently low frequencies. The mechanism of this turbulent absorption is attributed to the turbulent stress and the turbulent heat transfer acting on the coherent perturbations (including the sound waves) near the duct wall, i.e. sound-turbulence interaction.

The purpose of the current investigation is to understand the mechanism of the sound-turbulence interaction in low-Mach-number internal flows by theoretical modeling and numerical simulations. The turbulence absorption can be modeled through perturbation turbulent Reynolds stresses and perturbation turbulent heat flux in the linearized perturbation equations. In this thesis, the linearized perturbation equations are reviewed, and different models for the turbulent absorption of the sound waves are investigated. A new non–equilibrium model for the perturbation turbulent Reynolds stress is also proposed. The proposed model is validated by comparing with experimental data from the literature, and with the data from Direct Numerical Simulations (DNS) of pulsating turbulent channel flow. Good agreement is observed. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. viii, 82 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2015:30
Keyword
Aeroacoustics, Acoustic wave absorption, Acoustic wave propagation, Boundary layer turbulence, DNS
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-168031 (URN)978-91-7595-621-3 (ISBN)
Public defence
2015-06-15, D2, Lindstedtsvägen 5, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note

QC 20150526

Available from: 2015-05-26 Created: 2015-05-25 Last updated: 2015-05-26Bibliographically approved

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Weng, ChenyangBoij, SusannHanifi, Ardeshir

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