TY  - JOUR
A1  - Parezanovic, Vladimir
A1  - Cordier, Laurent
A1  - Spohn, Andreas
A1  - Duriez, Thomas
A1  - Noack, Bernd R.
A1  - Bonnet, Jean-Paul
A1  - Segond, Marc
A1  - Abel, Markus
A1  - Brunton, Steven L.
T1  - Frequency selection by feedback control in a turbulent shear flow
JF  - Journal of fluid mechanics
N2  - Many previous studies have shown that the turbulent mixing layer under periodic forcing tends to adopt a lock-on state, where the major portion of the fluctuations in the flow are synchronized at the forcing frequency. The goal of this experimental study is to apply closed-loop control in order to provoke the lock-on state, using information from the flow itself. We aim to determine the range of frequencies for which the closed-loop control can establish the lock-on, and what mechanisms are contributing to the selection of a feedback frequency. In order to expand the solution space for optimal closed-loop control laws, we use the genetic programming control (CPC) framework. The best closed-loop control laws obtained by CPC are analysed along with the associated physical mechanisms in the mixing layer flow. The resulting closed-loop control significantly outperforms open-loop forcing in terms of robustness to changes in the free-stream velocities. In addition, the selection of feedback frequencies is not locked to the most amplified local mode, but rather a range of frequencies around it.
KW  - free shear layers
KW  - instability control
KW  - turbulence control
Y1  - 2016
U6  - https://doi.org/10.1017/jfm.2016.261
SN  - 0022-1120
SN  - 1469-7645
VL  - 797
SP  - 247
EP  - 283
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
TY  - GEN
A1  - Parezanović, Vladimir
A1  - Cordier, Laurent
A1  - Spohn, Andreas
A1  - Duriez, Thomas
A1  - Noack, Bernd R.
A1  - Bonnet, Jean-Paul
A1  - Segond, Marc
A1  - Abel, Markus
A1  - Brunton, Steven L.
T1  - Frequency selection by feedback control in a turbulent shear flow
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Many previous studies have shown that the turbulent mixing layer under periodic forcing tends to adopt a lock-on state, where the major portion of the fluctuations in the flow are synchronized at the forcing frequency. The goal of this experimental study is to apply closed-loop control in order to provoke the lock-on state, using information from the flow itself. We aim to determine the range of frequencies for which the closed-loop control can establish the lock-on, and what mechanisms are contributing to the selection of a feedback frequency. In order to expand the solution space for optimal closed-loop control laws, we use the genetic programming control (CPC) framework. The best closed-loop control laws obtained by CPC are analysed along with the associated physical mechanisms in the mixing layer flow. The resulting closed-loop control significantly outperforms open-loop forcing in terms of robustness to changes in the free-stream velocities. In addition, the selection of feedback frequencies is not locked to the most amplified local mode, but rather a range of frequencies around it.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 572 
KW  - free shear layers
KW  - instability control
KW  - turbulence control
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-413693
SN  - 1866-8372
IS  - 572
ER  -