Resolvent analysis of self-sustained shock oscillations in transonic airfoil buffet

In this talk, we present the resolvent analysis of transonic airfoil buffet at a high Reynolds number using wall-resolved LES database to reveal the self-sustained mechanisms of shock oscillations. The resolvent analysis specifies the input-output relations in the buffet flowfield as forcing and response modes, and the two mechanisms of the self-sustained shock wave oscillations are identified. One mechanism is closely tied to the periodical change in shock-induced separation height that induces the pressure variations near the trailing edge. The other is related to the phenomenon that pressure variations behind the shock wave go around the shock and reach in front of the shock. Both the mechanisms lead to the changes in the shock-jump condition and thus the shock oscillations. The mechanisms identified by the resolvent analysis are also consistently confirmed by the high-fidelity LES flowfields.