The significance of coherent flow structures for the turbulent mixing ...

7.3 Spatio-temporal correlations with ¢¡¤£¦¥
To estimate the average decay of the flow structures being responsible for the production
of
§©¨¨
turbulence, the correlation was calculated, see right column of figure 7.11 and
7.13. The rapid § ¨¨ decay of for increasing is mainly caused by the small correlation
1
1
R uu
(∆t + =0)
0.8
0.6
0.4
0.2
R ww
(∆t + =0)
0.8
0.6
0.4
0.2
0
0
1
0
200
400 600
y + +∆y +
800
1000
−0.2
1
0
200
400 600
y + +∆y +
800
1000
R uu
(∆t + =2.3)
0.8
0.6
0.4
0.2
R ww
(∆t + =2.3)
0.8
0.6
0.4
0.2
0
0
1
0
200
400 600
y + +∆y +
800
1000
−0.2
1
0
200
400 600
y + +∆y +
800
1000
R uu
(∆t + =4.6)
0.8
0.6
0.4
0.2
R ww
(∆t + =4.6)
0.8
0.6
0.4
0.2
0
0
1
0
200
400 600
y + +∆y +
800
1000
−0.2
1
0
200
400 600
y + +∆y +
800
1000
R uu
(∆t + =23)
0.8
0.6
0.4
0.2
R ww
(∆t + =23)
0.8
0.6
0.4
0.2
0
0
0
200
400
600
y + +∆y +
800
1000
−0.2
0
200
400
600
y + +∆y +
800
1000
FIGURE ! #"%$
7.12: (left) )(( #"%$ and (right) correlation functions measured +*,.-0/1324242
at
5 -613287/924287:324287;3242877?4242@7AB2=287C32=287D3242@7/242=2 and (see location of the maximum).
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149