  The current work presents a realizable method to control streaky disturbances
in boundary layer flows and delay transition to turbulence via active flow
control. Numerical simulations of the nonlinear transitional regime in a
Blasius boundary layer are performed where streaks are excited in the boundary
layer via a high level of free-stream turbulence (FST). The occurring
disturbances are measured via localized wall sensors and damped via near-wall
actuators resembling plasma actuators. The time-varying amplitude of the signal
of each actuator is computed by processing signals from the sensors. This
processing is the result of two control laws: the Linear Quadratic Gaussian
regulator (LQG) and the Inverse Feed-Forward Control technique (IFFC). The use
of the first, LQG, requires a state-space representation of the system
dynamics, so the flow is described via an operator that captures only the most
relevant information of the dynamics and results in a reduced order model
(ROM). The ROM is computed via the eigensystem realization algorithm, based on
the impulse responses of the real system. Collecting such impulse responses may
be unfeasible when considering FST because of the high dimensionality of the
input forcing needed for a precise description of such a phenomenon. Here, a
new method to identify the relevant system dynamics and generate the needed
impulse responses is proposed, in a data-driven approach that would be
realizable in experiments. Finally, the effectiveness of the technique in
delaying bypass transition is shown. The work (i) presents a systematic way to
deal with high dimensional disturbances to build ROMs for a control technique,
and (ii) shows that even when considering constraints such as the type and size
of actuators and sensors, it is possible to achieve at least as large delay of
bypass transition as that obtained in more idealized cases found in literature.
