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

Abstract 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.

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