Adjoint based optimization and control of a separated boundary-layer flow

An adjoint based optimization procedure for the nonlinear Navier-Stokes system is implemented and applied to the dynamics of a separated boundary-layer flow over a bump. For this open flow configuration, boundary conditions which are compatible between the direct and adjoint system are implemented using the influence matrix technique. Beyond a critical Reynolds number, the flow is unstable and subject to instabilities with multiple time-scales. Computing iteratively optimal initial perturbations, the most sensitive regions to forcing are highlighted. Wall blowing-suction actuators are then introduced at these locations and their capability of controlling the unstable linear and nonlinear dynamics is explored, by means of the adjoint based numerical algorithm.