Regeneration and Self-Maintaining of Coherent Structures - Transport and Coherent Structures in Wall Turbulence - page 288

The key element in the mechanism of regeneration of the
HPVs in a laminar-base flow is the adverse pressure
gradient created upstream of a primary structure. The
intensity of the zone of depends on the Reynolds − ∂∂ px < 0

number

Γ

[5.12]

Re =

Γ

2 πν

where is the circulation of the vortex. A primary structure

with a Re

Γ

beyond a critical value causes a violent ejection of
fluid near to the wall toward the outer zone, by a mechanism
of unsteady separation which will be detailed later on. This
ejection regenerates secondary structures, which depend on
the severity of the inflectional profiles, on the one hand, and
the destabilization of the shear layer in the wake of the
primary structure, on the other hand. This process is
illustrated in Figure 5.10 and Figure 5.11.

Γ

Figure 5.10. Regeneration of hairpin structures by destabilization of the
shear layer in the wake of a primary structure