An adjoint-based drag reduction technique for unsteady flows

A framework based on a continuous adjoint-based analysis of steady and unsteady flows to predict control the drag force due surface morphing is presented. By establishing relation between perturbations in body shape boundary condition certain geometry, we derive an analytical expression sensitivity changes geometry its perturbation conditions. The methodology evaluated incompressible flow around cylinder for flows. reduction coefficient was obtained investigated by several deformations, conducted direction vector field solving derived adjoint problem. In flows, computed integrating problem backward time from solution. Two different types deformations calculated were applied: time-averaged deformation time-dependent. Attempting latter, at each step, did not yield same satisfactory results as terms expected reduction. We provide theoretical reasoning difference both methodologies, together with insight into physics distribution relating it sources.