Regeneration and Self-Maintaining of Coherent Structures - Transport and Coherent Structures in Wall Turbulence - page 340

Figure 5.30. Contours of fluctuations in streamwise velocity at t = 140
resulting from a wave packet disturbance where the parameters are
0.1 . The Reynolds number of the basic

flow is 3,005. The level of the fluctuations is

, , and ε = l == l 4

p = 2 q = 5

p

x z

. For a color version of
this figure, visit www.iste.co.uk/tardu/wallturbulence.zip

± 0.20

The mechanism of bypass transition is clearly nonlinear,
given that the forcing essentially stems from the wall-normal
velocity co m ponent which induces local mean stress
production uv . Remember that the transport equation for
the Reynolds stress in a homogeneous channel in the
streamwise and spanwise directions is

⎡ ⎤

∂ uv dU ∂ 1 ⎛ ∂ v ∂ u ⎞ ∂

⎢ ⎥

=− vv − uvv + p + − up

⎜ ⎟

∂ t dy ∂ y ρ ∂ x ∂ y ∂ y

⎢ ⎥

⎝ ⎠

⎣ ⎦

2

∂ uv ∂ u ∂ v

+ ν − 2 ν

2

∂ y ∂ x ∂ x

l l