Near-Wall Coherent Structures: History, Identification and Detection - Transport and Coherent Structures in Wall Turbulence - page 173

Figure 3.24. Bird's-eye view of the isosurfaces Δ= 0 in a turbulent

boundary layer at according to [CHA 96] and [CHA 00].

Re

θ =

670

( )

is
slight in the focal regions for reasons mentioned above.
It is linked primarily to the nodes-saddle points (stable or
unstable), and therefore to . Hence, the visualizations
performed by Chacin and Cantwell [CHA 00] show spatial
proximity between the dissipative events and the isocontours
. The small scales are undoubtedly responsible for ,
whose behavior depends closely on the large structures, by
way of the cascade process. The total kinetic energy
increases in focal zones with a longer lifetime because the

The dissipation εν∂ ∂ = ux u xux + ∂ ∂ ∂ ∂ = 2 ν ss

i j j i i j ij ij

Δ> 0

Δ< 0

Δ= 0

ε

ε

associated therewith is low. The dissipation becomes
significant in the regions where the focal points are in
juxtaposition, with the hypothesis being that is at quasi-

ε

equilibrium with production.