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

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5.3 Statistical properties of the flow
nation of the structure around the maximum of correlation and further away from this point.
As this correlation appears crestfallen, two different angles of attack can be estimated when
moving on the correlation ridge in up-stream and down-stream direction, and it can be seen
that the latter one is larger with respect to the other one for all locations of the fixed point.
The similarity between the size of ¼âÏ®Ï and ¼ÐÒHÒ in stream-wise direction and the elliptical
shape around the maximum, accompanied by the general variation of the angle with increasing
wall distance of the fixed point, implies a relation between both fluctuations. This might
be a result of a complex velocity structure (not necessarily a vortex structure) moving with
the fluid, but the exact relation cannot be seriously deduced from the correlation functions.
However, when the one-dimensional representations along the two coordinates through the
maximum of correlation in figure 5.9 and figure 5.10 are compared, this similarity vanishes
as the orientation of the principal axis of the ellipse around the span-wise coordinate differs
1
1
R uu
0.8
0.6
0.4
1
ï
0
200
ï
ï
400
∆x
ð +
600
ï
y
+ ò
=100
y
ò +
=200
y
ò +
=300
y
ò +
=400
y
+ ò
=500
y
ò +
=600
y
ò +
=700
y
+ ò
=800
ï
800
R uu
0.8
0.6
0.4
0.2
0
1
ï
0
200
ï
ï
400
y + +∆y + õ
600
ï
800
ï
R vv
0.8
0.6
0.4
0.2
0
1
ï
0
200
ï
ï
400
∆x +
600
ï
y + =100
y + =200
y + =300
y + =400
y + =500
y + =600
y + =700
y + =800
800
ï
R vv
0.8
0.6
0.4
0.2
0
1
ï
0
200
ï
ï
400
y + +∆y +
600
ï
800
ï
R ww
0.8
0.6
0.4
0.2
0
ï
0
200
ï
ï
400
∆x
ð +
600
ï
y =100
ò +
y =200
ò +
y =300
ò +
y =400
ò +
y =500
ò +
y =600
ò +
y =700
ò +
y =800
ò +
800
ï
R ww
0.8
0.6
0.4
0.2
0
−0.2
ï
0
200
ï
ï
400
y + +∆y + õ
600
ï
800
ï
FIGURE ç Ï®Ïlè ØUÚ Å/ÛeÜÝÅÛeÜŒÅÞ Ø ÜÝÅ*é 5.10: ç ÑÑŒè ØUÚ Å/ÛeÜÝÅÛeÜÝÅÞ Ø ÜÝÅé , ç Ò4Ò/è ØUÚ Å/ÛeÜŒÅ/ÛeÜÝÅöÞ Ø ÜŒÅêé
àߥߥß
and
.
measured at çNì
85
Ë!÷