Wall-bounded turbulent flows consist of multiple zones of relatively uniform streamwise velocity, known as uniform momentum zones (UMZs), separated by thin shear layers across which sharp velocity jumps occur. These zonal-like arrangements form a hierarchy consistent with the self-similar eddies postulated in Townsend’s attached-eddy hypothesis (AEH). However, whether the velocity fields carried by UMZs exhibit the asymptotic behaviours predicted by the AEH remains unclear because UMZs coexist over a wide range of scales. Here, we extract wall-scaled UMZs characterised by the wall-normal distance (y y y) and the friction velocity (u Subscript tau u τ u_), and examine the velocity fields within them in the context of the AEH. We analyse direct numerical simulation data of turbulent pipe flow at friction Reynolds numbers italic Re Subscript tau Baseline equals 550 Re τ = 550 Re_ = 550 – 6000 6000 6000. The number of UMZs increases logarithmically with italic Re Subscript tau Re τ Re_, while their interface velocities span a wide range, reflecting their hierarchical organisation. We identify wall-scaled UMZs exhibiting linear growth of thickness with y y y and velocity jumps scaled by u Subscript tau u τ u_. The turbulence statistics associated with these UMZs reveal a common wall-normal range, 5 italic Re Subscript tau Superscript negative 1 divided by 2 Baseline less than y divided by upper R less than 0. 2 <
Kim et al. (Tue,) studied this question.