Session AJ: Flow Control I
8:00 AM–10:10 AM, Sunday, November 21, 2010
Long Beach Convention Center Room: 201A
Chair: Joseph Katz, Johns Hopkins University
Abstract ID: BAPS.2010.DFD.AJ.8
Abstract: AJ.00008 : Feedback control of transition in boundary layer
9:31 AM–9:44 AM
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Abstract 
Authors:
Onofrio Semeraro
(Linne' Flow Centre, KTH Mechanics - Stockholm (SWE))
Shervin Bagheri
(Linne' Flow Centre, KTH Mechanics - Stockholm (SWE))
Luca Brandt
(Linne' Flow Centre, KTH Mechanics - Stockholm (SWE))
Dan S. Henningson
(Linne' Flow Centre, KTH Mechanics - Stockholm (SWE))
We study the use of feedback control for the delay of laminar-turbulent transition in boundary layer. The mitigation of three-dimensional wavepackets of streaks and Tollmien-Schlichting waves is investigated numerically. The dynamics is studied from an input-output point of view: a set-up of spatially localized inputs (external disturbances and actuators) and outputs (sensor for the estimation and objective functions) is introduced for the control design. Sensors and actuators are distributed in arrays near the wall, spanning the homogeneous spanwise direction. Reduced-order models of the Navier-Stokes equations including the inputs and outputs, obtained via balanced truncation, are used to design an LQG controller. The controller provides an optimal signal that minimizes the amplitude of the perturbation downstream. Using a limited number of sensors and actuators (about 10-20 elements), the linear controller reduces substantially the energy growth of the instabilities arising in the boundary layer flows. In the final contribution, the mitigation of finite-amplitude perturbations in nonlinear simulations and the delay of the laminar-turbulent transition will be addressed.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.DFD.AJ.8