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

æ
å
ä
¾
Ó
FIGURE 5.13: ç Ï®Ïlè ØUÚ Å/ÛeÜÝÅÛeÜŒÅÞ Ø ÜÝÅ*é , ç ÑÑŒè ØUÚ Å/ÛeÜÝÅÛeÜÝÅÞ Ø ÜÝÅé and ç Ò4Ò/è ØUÚ Å/ÛeÜŒÅ/ÛeÜÝÅöÞ Ø ÜŒÅêé
½
Â
æ
å
5 Investigation of the xy-plane
in the right column of figure 5.11 are strongly elongated close to the wall and it can be seen
that a remarkable region of negative correlation (dashed line) exists above the region of positive
correlation (solid line). For larger wall distances such a region of negative correlation
can be observed below the main structure but with reduced intensity. In addition it can be
seen that the main structure is slightly inclined relative to the stream-wise coordinate and that
the inclination angle increases in stream-wise direction. Figure
½
5.12
¾5À
shows
¢
a
½
comparison
¾©þ©¨
between
the investigations ¼×
performed at (solid symbols) and (opaque
¼×
¢
symbols). The left column reveals the stream-wise
þ¡
dependence
of
the
¢ ¢ ¢
primary correlations
measured at and the right column the Ä Å
corresponding dependence
on the location of the fixed point from the wall. Although the general dependence of the
correlations agrees fairly well when compared in wall-units, the correlation value of the high
R uu
1
0.8
0.6
0.4
0.2
R (uu)(uu)
1
0.8
0.6
0.4
0.2
0
1
ã
0
100
ã
ã
200
y + +∆y +
300
ã
400
ã
0
1
ã
0
100
ã
ã
200
y + +∆y +
300
ã
400
ã
0.8
0.8
R vv
0.6
0.4
0.2
R (vv)(vv)
0.6
0.4
0.2
0
1
ã
0
100
ã
ã
200
y + +∆y +
300
ã
400
ã
0
1
ã
0
100
ã
ã
200
y + +∆y +
300
ã
400
ã
0.8
0.8
R ww
0.6
0.4
0.2
R qq
0.6
0.4
0.2
0
ã
0
100
ã
ã
200
y + +∆y +
300
ã
400
ã
0
ã
0
100
ã
ã
200
y + +∆y +
300
ã
400
ã
(left), ç Ï'Ï Ï®Ï è ØUÚ Å ÛeÜ Å ÛeÜ Å Þ Ø Ü Å é , ç ÑÑ ÑÑ è ØÚ Å ÛeÜ Å ÛeÜ Å Þ Ø Ü Å é and ç è ØÚ Å ÛeÜ Å ÛeÜ Å Þ Ø Ü Å é
ߥß
(right) çNì
measured at . The maximum of correlation indicates the position of the fixed point
(same symbols as in figure 5.9).
88
ËBíî