Nonlinear response of vortex breakdown over a pitching delta wing

A flow visualization study was carried out to investigate the response of b reakdown location to small amplitude pitching oscillations of a delta wing, At moderate angles of attack, left and right breakdown locations are in-ph ase and locked to the pitching frequency, At large angles of attack, low-fr equency antisymmetric modes and the symmetric mode at the pitching frequenc y ant observed simultaneously. The existence of multiple frequencies in the spectra and other features suggest that vortex breakdown behaves like a no nlinear self excited oscillator.