Phase Averaging Analysis of the Unsteady Velocity Profiles in the Separation Flow on the Flat Plate

Abstract

Turbulent separated flow structure was studied by the phase averaging analysis to avoid the difficulty in the data acquisition of the phase angle of the time dependent signal with frequency modulation. This study proposed a new method of phase averaging by the wavelet transformation, and compared the results of the phase averaging by the wavelet transformation with those by the traditional phase averaging technique. These two techniques of the phase averaging, using the experimental data of the velocities in a periodically fluctuating separated flow, showed noticeable difference between their results. If the velocity signals include the frequency modulation, many shapes of velocity profiles by the traditional phase averaging technique will be nearly the same, and be similar to those of the time-averaged velocity. The wavelet transformation, however, showed the clear difference in the velocity profiles at each phase angle even for the velocity signals with modulated frequency.