Regeneration and Self-Maintaining of Coherent Structures - Transport and Coherent Structures in Wall Turbulence - page 284

counter-rotation in relation to the primary structures. The
wall certainly plays an important part in the process,
generating layers of vorticity with opposing sign to that of
the vortices convected near to it. Although the conceptual
“cartoon” analyzed here is instructive and reflects certain
characteristics of the regeneration process, we should not
overlook the fact that it is greatly simplified, and is devoid of
any wall effects.

5.3.2. Synthetic wall turbulence

We have already mentioned several times that the
foundational structure of wall turbulence is the hairpin
vortex (HPV), as suggested by Theodersen [THE 52] over 60
years ago. The vorticity lines near to the wall are spanwise,
and the vorticity com po nent which plays a predominant role
in the dynamics is . The raising of the spanwise

Ω+ ω

z z

∂
∂

v
z

vorticity by means of the term creates wall-normal

Ω

z

vorticity, as dictated by the following equation: 4

Figure 5.6. Profiles at . The parameters are

identical to those used for Figure 5.5

α =± 1

4 See Chapter 1.