Optimal control by blowing and suction at the wall of algebraically growing boundary layer disturbances

The upstream perturbations that maximize the spatial energy growth in a boundary layer are called optimal perturbations. The aim of the present paper is to find an optimal control by blowing and suction at the wall that minimizes the energy of perturbation, when the initial disturbance is itself optimal. The problem is examined by a method of receptivity analysis based on the numerical solution of the adjoint of the linearized boundary layer equations. We shall investigate both cases of a flat plate and a concave wall.