Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Feedback control of boundary layer bypass transition: experimental and numerical progress
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. 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.ORCID iD: 0000-0002-4346-4732
2009 (English)In: 47th AIAA Aerospace Sciences Meeting, Orlando, FL, American Institute of Aeronautics and Astronautics , 2009Conference paper, Published paper (Refereed)
Abstract [en]

Experimental and numerical work at the Linné FLOW Centre on active control of transition induced by free-stream turbulence is reviewed and two extensions to previous work are reported. Previously, an experimental setup with upstream sensors and downstream actuators has been built. It has been demonstrated that an 

ad-hoc  control algorithm is able to give a considerable attenuation of the disturbance amplitude downstream of the ac- tuators. Furthermore, large-eddy simulations (LES) of optimal feedback control have been performed for a similar flow configuration and disturbance attenuation as well as transition delay have been obtained. Two extensions are made. First, an effort is made to match the disturbance behavior in the experimental flow case and in the LES. Control is applied in simulations of the matched system aiming at approaching the type of actuation used in the experiments (localized suction). The control law is still computed as optimal feedback of the linear system. As the actuation ability approaches the experiments (where much simpler controllers were used), so does the control effect. Second, system identification (SI) is applied to the experimental data and a more efficient controller is designed. It is made plausible that controllers designed by SI can give considerable improvements in the disturbance attenuation. Implications for future work in the area of active control are discussed.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics , 2009.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-10647Scopus ID: 2-s2.0-78549262075OAI: oai:DiVA.org:kth-10647DiVA: diva2:222639
Conference
47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition, 5 - 8 January 2009, Orlando, Florida
Note
QC 20101020Available from: 2009-06-09 Created: 2009-06-09 Last updated: 2010-10-20Bibliographically approved
In thesis
1. Optimisation and control of boundary layer flows
Open this publication in new window or tab >>Optimisation and control of boundary layer flows
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Both optimal disturbances and optimal control are studied by means of numerical simulations for the case of the flat-plate boundary-layer flow. The optimisation method is the Lagrange multiplier technique where the objective function is the kinetic energy of the flow perturbations and the constraints involve the linearised Navier–Stokes equations. We consider both the optimal initial condition leading to the largest growth at finite times and the optimal time-periodic forcing leading to the largest asymptotic response. The optimal disturbances for spanwise wavelengths of the order of the boundary layer thickness are streamwise vortices exploiting the lift-up mechanism to create streaks. For long spanwise wavelengths it is the Orr mechanism combined with the amplification of oblique wave packets that is responsible for the disturbance growth. Control is applied to the bypass-transition scenario with high levels of free-stream turbulence. In this scenario low frequency perturbations enter the boundary layer and streamwise elongated disturbances emerge due to the non-modal growth. These so-called streaks are growing in amplitude until they reach high enough energy levels and breakdown into turbulent spots via their secondary instability. When control is applied in the form of wall blowing and suction, within the region that it is active, the growth of the streaks is delayed, which implies a delay of the whole transition process. Additionally, a comparison with experimental work is performed demonstrating a remarkable agreement in the disturbance attenuation once the differences between the numerical and experimental setup are reduced.

 

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. iii, 23 p.
Series
Trita-MEK, ISSN 0348-467X ; 2009:09
Keyword
boundary layer, control, estimation, optimal disturbances, Lagrange method
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-10652 (URN)978-91-7415-368-2 (ISBN)
Presentation
2009-06-15, Sal D42, KTH, Lindstedtsvägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-06-09 Created: 2009-06-09 Last updated: 2010-10-20Bibliographically approved

Open Access in DiVA

No full text

Other links

ScopusAIAA 2009-612

Authority records BETA

Brandt, Luca

Search in DiVA

By author/editor
Lundell, FredrikMonokrousos, AntoniosBrandt, Luca
By organisation
MechanicsLinné Flow Center, FLOW
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 53 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf