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Department of Mechanical and Aerospace Engineering
University of California, Los Angeles
Los Angeles, CA
Abstract-
Several recent studies have shown that controllers developed based on a linear
system theory work surprisingly well in reducing the viscous drag
in turbulent boundary layers, suggesting that the essential dynamics
of near-wall turbulence may well be approximated by a linearized
model. In our recent study, it was also shown that the linear coupling
term between the wall-normal velocity and wall-normal vorticity
terms in the linearized Navier-Stokes equations, which enhances
non-normality of the linearized system, also plays an important role
in maintaining near-wall turbulence in a fully developed turbulent flow.
Motivated by this rather surprising observation, linear controllers,
which are directly aimed at reducing the linear coupling term, have
been designed by employing
the linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG)
synthesis. The effect of
the linear term in a transitional and turbulent channel flows and the performance
of linear controllers designed to reduce the linear coupling term will
be presented.
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