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

7.2 Statistical properties of the log-law region
7.2.1 Spatial correlations with ²L³¢´Tµ
The following sequence of figures reveals for ª«§_¬3®c¯ the three primary correlations of
the velocity fluctuations for various wall distances of the fixed point as indicated it the caption
or by the location of the maximum. The distance between the contour levels is 0.05 and
the solid lines indicate a positive correlation value. Clearly visible is the different size and
shape of the correlations and the variation with the wall distance. While the ªS··¥¸º¹&» Š ¹¥»"¼
» Š ÍeÏ »¾½ correlation, shown in figure 7.5, is nearly circular in shape for ¹ »
¡À¿
Ír¹
of the correlation measured ¹&»Á¬A at (upper left plot) decreases quite rapidly in span-wise
direction. The extention in wall-normal direction on the other hand measures several hundred
wall-units. The short width of the correlation à » in -direction implies the relation with the near-
, the size
R (y
+
=30)
uu
R (y
+
=200)
uu
y + ∆ y
+
y + ∆ y
+
y + ∆ y
+
R (y
+
=50)
uu
R (y
+
=300)
uu
R (y
+
=100)
uu
R (y
+
=400)
uu
∆ z +
∆ z
+
FIGURE ˜ ·$·ÅÄ © »ÇÆ © » ÈÊÉ © »‹ÆËÉÌZ»¾Í 7.5: correlation measured © » at
(upper left to lower right).
š4Χž ÆËÏ ž ÆÐ žž ÆËÑ žž Æ Îžž ÆÓÒ žž
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