Modal analysis of transonic shock buffet on 2d airfoil

The paper presents a study of the shock buffet phenomenon on the RA16SC1 supercritical airfoil using the Proper Orthogonal Decompo- sition (POD) and Dynamic Mode Decomposition (DMD) modal ap- proaches. A validation of the computational tool is presented and the full buffet envelope of the RA16SC1 airfoil is mapped. POD and DMD techniques are applied to compute a set of ow modes and corresponding dynamical data (for the DMD method). A neutrally stable domifinant buffet mode is identfied at the buffet frequency. The correspond- ing mode shape represents the interaction between the shock wave and boundary layer. Higher modes, at multiples of the buffet frequency, show coherent ow structures at the shock travel area. Further higher modes, of mixed frequencies, are associated with ow structures mainly in the boundary layer area. Only a few modes are required for sufficiently accurate reconstruction of the buffet ow field. Similar modes were computed for all buffet angles-of-Attack. The modal approach used in this study enables straight forward extraction of the underlying ow structures and dynamic properties of buffet ows.