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

6 Investigation of the xz-plane
300
250
200
z
+
150
100
50
0
0 50 100 150 200 250 300 350 400 450 500 550
300
y [???]
250
x [???]
200
z
+
150
100
50
0
0 50 100 150 200 250 300 350 400 450 500 550
x
+
y [???]
FIGURE 6.29: Vorticity fluctuation calculated from figure 6.28.
x [???]
is approximately © Çcb
, according to the previous figures, the projection of the cross-section in
stream-wise direction is roughly 42 wall-units. Thus, the variation of the length can be estimated
to ª¥À¢À¢À ¸ © ¨ Ê
investigation. However, in contrast to the hot wire results, the maximum of the graphs shown
in the left image of figure 6.30 always appears on the left hand side from the minimum while
in the results presented in [102] the maximum appears on the right hand side. This can be
explained by the different representations. While in [102] the pattern is displayed against the
time and here against the spatial coordinate, a small time in [102] correspond to a large downstream
position. So when the time axis of the hot wire results is reversed for comparison, the
132
¨ © which nicely corresponds with the result deduced from the hot wire