RÉSUMÉ

In the present study, we develop a method for controlling absolute instability based on variational calculus. In parallel wake exhibiting absolutely unstable nature, it is shown that the positive and negative velocity perturbations in basic flow, respectively, along the centerline and the separating shear layers suppress absolute instability. Using this method, we show that a secondary cylinder located at appropriate positions in the wake behind a main circular cylinder effectively suppress absolute instability in the near wake. It is also shown that the most effective position of the secondary cylinder suppressing absolute instability is along the separating shear layer.