Investigating intermittency in turbulent channel and wake flows using a novel time-frequency-based method

Intermittent flow behaviors are commonly observed in turbulent flows. In general, this intermittency is associated with enhanced mixing and non-linear, chaotic behavior. Thus, investigating intermittency will reveal the non-uniform energy dissipation mechanism present in turbulent flows. In this work, we investigate the underlying energy dissipation mechanism associated with intermittency in both turbulent channel flow and wake flows using time-frequency analysis. A direct numerical simulation (DNS) dataset of channel flow over a rough wall surface and an experimental stereoscopic particle image velocimetry (PIV) dataset of wake flow over a cylindrical bluff body are considered. We extracted both instantaneous and spatially localized frequencies of the flows using our novel time-frequency method: the Fourier-decomposition wavelet transform. Further, we investigated the associated localized energy cascade and the corresponding scaling range to understand the scaling mechanism present in these turbulent flows. Finally, the extracted localized frequency structures are compared with traditional coherent structures to understand the energy dissipation pattern.