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State estimation in wall-bounded flow systems: P. II Turbulent flows
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0001-7864-3071
2006 (English)In: Journal of fluid mechanics, ISSN 0022-1120, Vol. 552, 167-187 p.Article in journal (Refereed) Published
Abstract [en]

This work extends the estimator developed in Part I of this study to the problem of estimating a turbulent channel flow at Re-tau=100 based on a history of noisy measurements on the wall. The key advancement enabling this work is the development and implementation of an efficient technique to extract, from direct numerical simulations, the relevant statistics of an appropriately defined 'external forcing' term on the Navier-Stokes equation linearized about the mean turbulent flow profile. This forcing term is designed to account for the unmodelled (nonlinear) terms during the computation of the (linear) Kalman filter feedback gains in Fourier space. Upon inverse transform of the resulting feedback gains computed on an array of wavenumber pairs to physical space, we obtain, as in Part 1, effective and well-resolved feedback convolution kernels for the estimation problem. It is demonstrated that, by applying the feedback so determined, satisfactory correlation between the actual and estimated flow is obtained in the near-wall region. As anticipated, extended Kalman filters (with the nonlinearity of the actual system reintroduced into the estimator model after the feedback gains are determined) outperform standard (linear) Kalman filters on the full system.

Place, publisher, year, edition, pages
2006. Vol. 552, 167-187 p.
Keyword [en]
Feedback-Control, Transition, Channel
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-5627DOI: 10.1017/S0022112005008578ISI: 000237161500009Scopus ID: 2-s2.0-33645345695OAI: oai:DiVA.org:kth-5627DiVA: diva2:10056
Note
QC 20100830Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2010-12-06Bibliographically approved
In thesis
1. Stability and control of shear flows subject to stochastic excitations
Open this publication in new window or tab >>Stability and control of shear flows subject to stochastic excitations
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

In this thesis, we adapt and apply methods from linear control theory to shear flows. The challenge of this task is to build a linear dynamic system that models the evolution of the flow, using the Navier--Stokes equations, then to define sensors and actuators, that can sense the flow state and affect its evolution. We consider flows exposed to stochastic excitations. This framework allows to account for complex sources of excitations, often present in engineering applications. Once the system is built, including dynamic model, sensors, actuators, and sources of excitations, we can use standard optimization techniques to derive a feedback law. We have used feedback control to stabilize unstable flows, and to reduce the energy level of sensitive flows subject to external excitations.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 86 p.
Series
Trita-MEK, ISSN 0348-467X ; 2006:08
Keyword
control, estimation, stochastic excitations, feedback, model reduction
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-3929 (URN)
Public defence
2006-05-05, Sal F3, Lindstedtsvägen 26, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20100830Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2011-12-16Bibliographically approved

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Henningson, Dan

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