Second-order sensitivity in the cylinder wake: Optimal spanwise-periodic wall actuation and wall deformation

  title={Second-order sensitivity in the cylinder wake: Optimal spanwise-periodic wall actuation and wall deformation},
  author={Edouard Boujo and Andrea S. Marcano Fani and François Gallaire},
  journal={Physical Review Fluids},
Two-dimensional (2D) flows are efficiently controlled with spanwise waviness, i.e. spanwise-periodic (SP) wall blowing/suction/deformation. We tackle the global linear stability of 2D flows subject to small-amplitude 3D SP control. Building on previous work for parallel flows (Boujo et al. 2015), an adjoint method is proposed for computing the 2nd-order eigenvalue sensitivity. Such control has a zero 1st-order linear effect, so the 2nd-order quadratic effect prevails. The sensitivity operator… 

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