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SUMMARY:Resolvent-based estimation and control of turbulent shear flows - 
 Aaron Towne (University of Michigan)
DTSTART:20220330T110000Z
DTEND:20220330T113000Z
UID:TALK171188@talks.cam.ac.uk
DESCRIPTION:Flow estimation and control provide a path forward toward achi
 eving many important engineering objectives\, such as decreasing drag\, de
 laying flow separation and transition\, and reducing flow-generated noise.
  While state estimation and control are classical topics in dynamical syst
 ems and control theory\, standard methods have several disadvantages when 
 applied to turbulent flows\, including high cost and restrictions in their
  ability to incorporate key physics. In this presentation\, I will describ
 e an alternative framework for optimal flow estimation and control formula
 ted in terms of resolvent operators obtained from the Navier-Stokes equati
 ons\, which have been shown to efficiently describe organized motions with
 in turbulent flows. The resolvent-based framework provides a hierarchy of 
 methods for different tasks\, including space-time statistical modeling\, 
 flow-field reconstruction in the time domain\, real-time causal estimation
 \, and control. When equivalent assumptions are made\, the causal resolven
 t-based estimator and controller reproduce the Kalman filter and LQG contr
 oller\, respectively\, but at substantially lower computational cost. Unli
 ke these methods\, the resolvent-based approach can naturally accommodate 
 forcing terms (nonlinear terms from Navier-Stokes) with colored-in-time st
 atistics\, which significantly improves the accuracy of the estimates. Mor
 eover\, the use of the resolvent framework facilitates physical interpreta
 tion of the mechanisms involved in the estimation and control procedure in
  terms of coherent flow structures. The performance of the resolvent-based
  methods is demonstrated using the flow over a backward-facing step and a 
 turbulent channel flow.&nbsp\;
LOCATION:Seminar Room 1\, Newton Institute
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