dc.description.abstract |
Suppression of the transient energy growth in subcritical plane Poiseuille flow
via feedback control is addressed. It is assumed that the time derivative of any
of the velocity components can be imposed at the walls as control input and that
full-state information is available. We show that it is impossible to design a
linear state-feedback controller that leads to a closed-loop flow system without
transient energy growth. In a subsequent step, state-feedback controllers-
directly targeting the transient growth mechanism-are designed using a procedure
based on a linear matrix inequalities approach. The performance of such
controllers is analyzed first in the linear case, where comparison to previously
proposed linear-quadratic optimal controllers is made; further, transition
thresholds are evaluated via direct numerical simulations of the controlled
three-dimensional Poiseuille flow against different initial conditions of
physical interest, employing different velocity components as wall actuation.
The present controllers are effective in increasing the transition thresholds in
closed loop, with varying degree of performance depending on the initial
condition and the actuation component employed. |
en_UK |