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 three-dimensional optimal disturbances using reduced-order models
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control.
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control.ORCID iD: 0000-0002-8209-1449
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control.ORCID iD: 0000-0002-4346-4732
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control.ORCID iD: 0000-0001-7864-3071
2011 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 677, 63-102 p.Article in journal (Refereed) Published
Abstract [en]

The attenuation of three-dimensional wavepackets of streaks and Tollmien-Schlichting (TS) waves in a transitional boundary layer using feedback control is investigated numerically. Arrays of localized sensors and actuators (about 10-20) with compact spatial support are distributed near the rigid wall equidistantly along the spanwise direction and connected to a low-dimensional (r = 60) linear quadratic Gaussian controller. The control objective is to minimize the disturbance energy in a domain spanned by a number of proper orthogonal decomposition modes. The feedback controller is based on a reduced-order model of the linearized Navier-Stokes equations including the inputs and outputs, computed using a snapshot-based balanced truncation method. To account for the different temporal and spatial behaviour of the two main instabilities of boundary-layer flows, we design two controllers. We demonstrate that the two controllers reduce the energy growth of both TS wavepackets and streak packets substantially and efficiently, using relatively few sensors and actuators. The robustness of the controller is investigated by varying the number of actuators and sensors, the Reynolds number and the pressure gradient. This work constitutes the first experimentally feasible simulation-based control design using localized sensing and acting devices in conjunction with linear control theory in a three-dimensional setting.

Place, publisher, year, edition, pages
2011. Vol. 677, 63-102 p.
Keyword [en]
boundary layer stability, control theory, flow control
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
URN: urn:nbn:se:kth:diva-36235DOI: 10.1017/S0022112011000620ISI: 000292095200003Scopus ID: 2-s2.0-79959256638OAI: oai:DiVA.org:kth-36235DiVA: diva2:430633
Funder
Swedish e‐Science Research Center
Note
Updated from submitted to published. QC 20120328Available from: 2011-07-11 Created: 2011-07-11 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Feedback control and modal structures in transitional shear flows
Open this publication in new window or tab >>Feedback control and modal structures in transitional shear flows
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

 

Two types of shear flows are investigated in this thesis; numerical simulations are performed for the analysis and control of the perturbation arising in a boundary layer over a flat plate, whereas PIV measurements are analysed for the investigation of a confined turbulent jet. Modal structures of the flows are identified: the aim is to understand the flow phenomena and to identify reduced-order models for the feedback control design. The attenuation of three-dimensional wavepackets of streaks and Tollmien-Schlichting (TS) waves in the boundary layer is obtained using feedback control based on arrays of spatially localized sensors and actuators distributed near the rigid wall. In order to tackle the difficulties arising due to the dimension of the discretized Navier-Stokes operator, a reduced-order model is identified, preserving the dynamics between the inputs and the outputs; to this end, approximate balanced truncation is used. Thus, control theory tools can be easily handled using the low-order model. We demonstrate that the energy growth of both TS wavepackets and streak-packets is substantially and efficiently mitigated, using relatively few sensors and actuators. The robustness of the controller is investigated by varying the number of actuators and ensors, the Reynolds number and the pressure gradient. The configuration can be possibly reproduced in experiments, due to the localization of sensing and actuation devices. A complete analysis of a confined turbulent jet is carried out using timeresolved PIV measurements. Proper orthogonal decomposition (POD) modes and Koopman modes are computed and analysed for understanding the main features of the flow. The frequencies related to the dominating mechanisms are identified; the most energetic structures show temporal periodicity.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. vii, 33 p.
Series
Trita-MEK, ISSN 0348-467X ; 2011:01
Keyword
flow control, flat-plate boundary layer, laminar-turbulent transition
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-29754 (URN)978-91-7415-863-2 (ISBN)
Presentation
2011-02-18, Sal E3, KTH, Osquars backe 14, Stockhkolm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish e‐Science Research Center
Note
QC 20110214Available from: 2011-02-14 Created: 2011-02-14 Last updated: 2012-05-24Bibliographically approved
2. Active Control and Modal Structures in Transitional Shear Flows
Open this publication in new window or tab >>Active Control and Modal Structures in Transitional Shear Flows
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Flow control of transitional shear flows is investigated by means of numerical simulations. The attenuation of three-dimensional wavepackets of Tollmien-Schlichting (TS) and streaks in the boundary layer is obtained using active control in combination with localised sensors and actuators distributed near the rigid wall. Due to the dimensions of the discretized Navier-Stokes operator, reduced-order models are identified, preserving the dynamics between the inputs and the outputs of the system. Balanced realizations of the system are computed using balanced truncation and system identification.

We demonstrate that the energy growth of the perturbations is substantially and efficiently mitigated, using relatively few sensors and actuators. The robustness of the controller is analysed by varying the number of actuators and sensors, the Reynolds number, the pressure gradient and by investigating the nonlinear, transitional case. We show that delay of the transition from laminar to turbulent flow can be achieved despite the fully linear approach. This configuration can be reproduced in experiments, due to the localisation of sensing and actuation devices.

The closed-loop system has been investigated for the corresponding twodimensional case by using full-dimensional optimal controllers computed by solving an iterative optimisation based on the Lagrangian approach. This strategy allows to compare the results achieved using open-loop model reduction with model-free controllers. Finally, a parametric analysis of the actuators/ sensors placement is carried-out to deepen the understanding of the inherent dynamics of the closed-loop. The distinction among two different classes of controllers – feedforward and feedback controllers - is highlighted.

A second shear flow, a confined turbulent jet, is investigated using particle image velocimetry (PIV) measurements. Proper orthogonal decomposition (POD) modes and Koopman modes via dynamic mode decomposition (DMD) are computed and analysed for understanding the main features of the flow. The frequencies related to the dominating mechanisms are identified; the most energetic structures show temporal periodicity.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. vii, 72 p.
Series
Trita-MEK, ISSN 0348-467X ; 2013:03
Keyword
Flow control, flat-plate boundary layer, optimal controllers, model reduction, turbulent jet, POD, DMD, Koopman modes
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-117916 (URN)978-91-7501-640-5 (ISBN)
Public defence
2013-02-22, Sal E3, Osquars Backe 14, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20130207

Available from: 2013-02-07 Created: 2013-02-07 Last updated: 2013-02-07Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Bagheri, ShervinBrandt, LucaHenningson, Dan Stefan

Search in DiVA

By author/editor
Semeraro, OnofrioBagheri, ShervinBrandt, LucaHenningson, Dan Stefan
By organisation
Stability, Transition and Control
In the same journal
Journal of Fluid Mechanics
Other Engineering and Technologies not elsewhere specified

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 334 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