A Self-Contained, Automated Methodology for Optimal Flow Control

This paper describes a self-contained automated methodology for active flow control which couples the time-dependent Navier-Stokes system with an adjoint Navier-Stokes system and optimality conditions from which optimal states, i.e., unsteady flow fields and controls (e.g., actuators), may be determined. The problem of boundary-layer instability suppression through wave cancellation is used as the intital validation case to test the methodology. Here, the objective of control is to match the stress vector along a portion of the boundary to a steady base flow. Control is effected through the injection or suction of fluid through a single orifice on the boundary. The results demonstrate that instability suppression can be achieved without any a priori knowledge of the flow unsteadiness such as frequencies, instability type, etc. The present methodology has been extended to three dimensions and may potentially be applied to separation control, relaminarization, and turbulence control applications using one to many sensors and actuators.