caa a22 4500 606198156 CHVBK 20210128100932.0 cr unu---uuuuu 210128e20151001xx s 000 0 eng 10.1007/s00348-015-2058-8 doi (NATIONALLICENCE)springer-10.1007/s00348-015-2058-8 Wavelet analysis of wall turbulence to study large-scale modulation of small scales [Elektronische Daten] [W. Baars, K. Talluru, N. Hutchins, I. Marusic] Wavelet analysis is employed to examine amplitude and frequency modulations in broadband signals. Of particular interest are the streamwise velocity fluctuations encountered in wall-bounded turbulent flows. Recent studies have shown that an important feature of the near-wall dynamics is the modulation of small scales by large-scale motions. Small- and large-scale components of the velocity time series are constructed by employing a spectral separation scale. Wavelet analysis of the small-scale component decomposes the energy in joint time-frequency space. The concept is to construct a low-dimensional representation of the small-scale time-varying spectrum via two new time series: the instantaneous amplitude of the small-scale energy and the instantaneous frequency. Having the latter in a time-continuous representation allows a more thorough analysis of frequency modulation. By correlating the large-scale velocity with the concurrent small-scale amplitude and frequency realizations, both amplitude and frequency modulations are studied. In addition, conditional averages of the small-scale amplitude and frequency realizations depict unique features of the scale interaction. For both modulation phenomena, the much studied time shifts, associated with peak correlations between the large-scale velocity and small-scale amplitude and frequency traces, are addressed. We confirm that the small-scale amplitude signal leads the large-scale fluctuation close to the wall. It is revealed that the time shift in frequency modulation is smaller than that in amplitude modulation. The current findings are described in the context of a conceptual mechanism of the near-wall modulation phenomena. Springer-Verlag Berlin Heidelberg, 2015 Baars W. Department of Mechanical Engineering, University of Melbourne, 3010, Parkville, VIC, Australia aut Talluru K. Discipline of Mechanical Engineering, University of Newcastle, 2308, Newcastle, NSW, Australia aut Hutchins N. Department of Mechanical Engineering, University of Melbourne, 3010, Parkville, VIC, Australia aut Marusic I. Department of Mechanical Engineering, University of Melbourne, 3010, Parkville, VIC, Australia aut Experiments in Fluids Springer Berlin Heidelberg 56/10(2015-10-01), 1-15 0723-4864 56:10<1 2015 56 348 https://doi.org/10.1007/s00348-015-2058-8 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00348-015-2058-8 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Baars W. Department of Mechanical Engineering, University of Melbourne, 3010, Parkville, VIC, Australia aut NATIONALLICENCE 700 1- Talluru K. Discipline of Mechanical Engineering, University of Newcastle, 2308, Newcastle, NSW, Australia aut NATIONALLICENCE 700 1- Hutchins N. Department of Mechanical Engineering, University of Melbourne, 3010, Parkville, VIC, Australia aut NATIONALLICENCE 700 1- Marusic I. Department of Mechanical Engineering, University of Melbourne, 3010, Parkville, VIC, Australia aut NATIONALLICENCE 773 0- Experiments in Fluids Springer Berlin Heidelberg 56/10(2015-10-01), 1-15 0723-4864 56:10<1 2015 56 348