Separating adverse-pressure-gradient and Reynolds-number effects in turbulent boundary layers

Wall turbulence is characterized by a near-wall cycle of streaks and quasistreamwise vortices apparent as an invariant inner peak in the premultiplied energy spectra. A second, outer peak is known to emerge in this spectral view and become energized with increasing Reynolds number (Re) as well as adverse pressure gradient (APG). An analysis of experimental data sets examines how this outer peak scales with Re and APG and whether their imprint on the near-wall small scales are different.