Regeneration and Self-Maintaining of Coherent Structures - Transport and Coherent Structures in Wall Turbulence - page 302

the wall, and to reveal the rather dominant role of linearity
in the development of the wall structure, does hold a certain
interest. In addition, it would be advantageous to verify
whether these elements can (at least partly) account for the
success of linear control of turbulent drag [KIM 07].

y +

Figure 5.14. a) Contours of the streamwise velocity in the plane ,

resulting from asymmetrical nonlinear forcing, after a period
approximately equal to the period of the ejections. This figure is adapted
from [LAN 90]. b) Conditional contours obtained at

= 15

y +

by direct

= 15

numerical simulations in a channel flow at , according to

Re
τ

= 180

[JOH 91]

[HAR 89] employs a simplified version of Landahl's model
to predict the distribution of the Reynolds stresses in the
inner layer. Pra nd tl's model is not modified for the
component ul . However, the wall-normal velocity

is considered to be the exact material derivative of l with
vDlDt

=− ∂∂ Uy

. The Reynolds stress is then

=

1
2

Dl

2

∂
∂

U

[5.43] −= uv

2

Dt y