The Bump Suppression Strategy for the Transonic Buffet of the Supercritical Airfoil

Transonic buffet brings challenges to civil aircraft design, including but not limited to the structural fatigue and the handling quality degradation. Therefore, it is necessary to analyze the transonic buffet of the supercritical airfoil and propose the buffet suppression strategy. This paper first employs the delayed detached-eddy simulation method to simulate the unsteady buffet process of the OAT15A supercritical airfoil. Then, the temporal-spatial characteristics of the flowfield and the separation region dynamics are analyzed based on the time-domain analysis method and the dynamic mode decomposition method. After that, different two-dimensional bumps are arranged in the shock motion region to suppress the shock oscillation, and the suppression mechanism and suppression strategy are studied. The results show that the process of the developed transonic buffet is significantly influenced by the merging of the front and the rear separation regions. In case the bump obstructs this confluence phenomenon, the developed transonic buffet can be suppressed. Furthermore, it is also found that a two-dimensional bump with superior buffet performance should have the following features: The bump should be placed after the shock-induced boundary-layer separation point to make the shock-induced boundary-layer separation bubble generate on the bump ramp. Also, the height of the bump should be carefully designed to prevent the front and rear separation regions from merging and to make the front separation region disappear quickly. Finally, this strategy is successfully applied to another supercritical airfoil to confirm the universality of the controlling strategy proposed.