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

6.2 Statistical properties of the buffer layer
moves to negative stream-wise displacements, particularly if the ÃË correlation is considered.
For clarity, the two lower rows of figure 6.9 reveal the functional dependence of the
correlations along the axis of symmetry. This representation allows to compare the height
of the correlation and the location of the maximum in detail. Figure 6.11 shows the twodimensional
spatial cross-correlation function of negative stream-wise fluctuations with the
span-wise velocity component à î Ñ ¹ Í5Î ® Á ­.® Á ÍlÏ ® ¼ (left) and correlation positive streamwise
fluctuations with span-wise components à ® Ñ ¹ Í Î ® Á ­® Á–ÍeÏ ® ¼ (right). Figure 6.12 displays
the corresponding function of positive wall-normal fluctuations (extracted from flow
regions where §ôºóÀ ) with the span-wise velocity component à ® Ë ¹ Í5Î ® Á ­ ® Á–ÍeÏ ® ¼ (left) and
correlation of negative wall-normal fluctuations (extracted from flow regions where §!½þÀ )
with span-wise components ÃË with ¹|· º»À¼ (right). These structures permit to resolve the
+
R (+v)(w) (y =30)
+
R (-v)(w) (y =30)
∆ z +
∆ z +
∆ z
+
+
R (+v)(w) (y =20)
+
R (+v)(w) (y =10)
R (-v)(w)
+
(y =20)
R (-v)(w)
+
(y =10)
∆x + ∆x +
FIGURE 6.12: Conditional cross-correlation of positive wall-normal fluctuations (extracted from flow
regions where
Ø
) with the span-wise velocity component Ð ê Ë 3ìÌí ê í (left) and correlation of negative
wall-normal fluctuations (extracted from flow regions where "!
Ø
) with span-wise components
Ð ê Ë ë3ìÌí ê í (right) measured at ИÅ# û§¥Ø¡Ø
and Ó ® ֥آÙÛÚ¥Ø¢Ù Ü Ø
(top to bottom).
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