The first figure illustrates the suppression of the instability present in the uncontrolled flow. We plot the peturbation (from Blasius flow) of the horizontal component of velocity vs. distance normal to the wall. The curve with circles is for the uncontrolled flow while the curve with the filled squares is for the controlled flow. We see that the optimal control strategy has effected a very substantial reduction in the deviation from Blasius flow.
The third curve, the one with diamonds, is for a case in which control is turned on for a while and then turned off. (All three plots are for the same instant in time.) We see that turning off the control will allow the flow to again become unstable.
The second figure is analogous to the first but for the vertical component of velocity.
Convergence of the forward state-backward adjoint sweep strategy