Shape optimization to improve the transonic fluid-structure interaction stability by an aerodynamic unsteady adjoint method

A kind of single degree-of-freedom (SDOF) flutter, which is also called transonic buzz, would appear on the aircraft control surface in a specific transonic state. Engineers deal with control surface buzz mainly by improving the stiffness or damping of the structure. Traditional adjoint-based aerodynamic shape optimizations mainly focus on the aircraft aerodynamic performance. In this paper, the unsteady adjoint method is employed to improve the transonic fluid-structure interaction (FSI) stability from the viewpoint of aerodynamic shape optimization. To achieve this aim, the aerodynamic damping derivative, which represents the work done by flow to structure, is adopted as the objective of shape optimization. Results show that through the airfoil shape optimization, the FSI stability of the control surface is remarkably improved, and the buzz is eliminated successfully in design conditions. In addition, the aerodynamic performance of the control surface is also refined.