Civil Engineering Reference
In-Depth Information
The increase of the streamwise intensity with increasing
Re
is thus caused directly by the effect engendered by the
passive structures. However, Figure 4.28 clearly suggests
that
⎛
⎝
⎞
⎠
*
max
is approximately independent of the
Reynolds number, with
⎜
⎟
u
P
u
P
(
)
(
)
u
*
PP
+
uu
=
C
=
uu
U
τ
uP
PP
max
max
max
c
This relation is expressed by
(
)
U
1
+
uu
=
C
c
=
C
[4.39]
()
PP
up
up
u
ς
h
+
max
max
max
τ
The constant
C
up
max
has a value of 0.38, according to the
results given in Figure 4.28. The
()
ς
+
function is analyzed
in detail in section 4.5 in [TAR 11a, TAR 11b]. The
asymptotic form in the boundary
h
+
h
()
of
+
is
→∞
ς
h
1
()
−
1
+
+
ς
h
=
ln
h
+
H
κ
∞
∞
according to [WOS 00]. The empirical values of the
parameters appearing in this relation are, respectively,
κ
∞
=
8.5
. By substituting these values back
into equation [4.39], we find
0.4
and
H
∞
=
)
)
max
(
(
+
+
[4.40]
uu
∝
u u
∝
0.95ln
h
+
Pp
max
This last relation is practically identical to the empirical
equation [4.36]. The model advanced by [PAN 07], although
it is conceptually simple, is capable of predicting the
Search WWH ::
Custom Search