Abstract
The vortex structures in a separated flow region are generated by the motion of the separated shear layer caused by the introduction of periodic fluctuation. The main cause of the motion of the separated shear layer is the external fluctuation with the characteristic frequency. In order to investigate the principle motion of the velocity field, phase averaging was conducted to the velocity signals obtained by single hot-wire measurement. In phase averaging, wavelet transformation was applied to obtained the dominant frequency and the characteristic phase angle in the fluctuation. The profiles of the averaged velocity could be found and discussed. The profiles vary dynamically at each phase angle and show the periodic motion of the shear layer. The separated shear layer flutters with the external fluctuation in the mean flow. If the suitable frequency is selected in the external fluctuation, the separated flow region disappears in almost all phase angles owing to the depression of the shear layer near the wall.
