Adjoint Sensitivity Analysis of Low-Speed Flows Using an Efficient Harmonic Balance Technique.

The article presents a study of the adjoint sensitivity of unsteady low-speed flows using an efficient time-spectral harmonic balance approach. The study used a finite-difference approach to assess the accuracy of the adjoint senstivities. It suggests that the cost can be up to 3-5 times the cost of a single computational fluid dynamics (CFD) run when the number of design variables is in hundreds.