Session IB: Invited Lecture: The Use of Global Modes to Understand Transition and Perform Flow Control
3:30 PM–4:10 PM, Monday, November 20, 2006
Tampa Marriott Waterside Hotel and Marina Room: Grand Salon F
Chair: Thomas Corke, University of Notre Dame
Abstract ID: BAPS.2006.DFD.IB.1
Abstract: IB.00001 : The use of global modes to understand transition and perform flow control
3:30 PM–4:10 PM
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Author:
Dan Henningson
(Mechanics KTH Sweden)
The stability of highly non-parallel flows are considered using superposition of global modes. When purturbed by the worst case initial condition these flows often exhibits a large transient growth associated with the development of wavepackets. The global modes of the systems also provides a good starting point for the design of reduced order models used to control the growing disturbances. As the main example, the control of a globally unstable boundary-layer flow along a cavity is considered. The disturbance development is associtated with the development of a wavepacket along the cavity shear layer followed by a global cycle related to the two unstable global modes. Direct numerical simulations of this flow are coupled to a measurement feedback controller, which senses the wall shear stress at the downstream lip of the cavity and provides the actuation at the upstream lip. A reduced order model for the control is obtained by a projection on the least stable global eigenmodes. The LQG controller is run in parallel to the Navier-Stokes time integration and it is shown to damp out the global oscillations.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.DFD.IB.1