
Sunden CH009.tex 25/8/2010 10: 57 Page 370
370 Computational Fluid Dynamics and Heat Transfer
Although the permeable-wall version of the AWF does not need to resolve
the region inside a permeable wall, by non-linearly linking to the solution of the
modified Brinkman equations for the flows inside porous media, it can bridge
the flows inside and outside of the porous media successfully. Since the com-
putedturbulentflowfieldsoverpermeableporoussurfacesarereasonably inaccord
with the corresponding data, theAWF for permeable wall turbulence models such
complicated wall-flow interactions.
By linking to the correct near-wall variation of turbulent viscosity µ
t
∝ y
3
,
the AWF can be successfully applicable to flows over a wide range of Prandtl
numbers up to Pr=4×10
4
, for smooth wall cases. (For flow fields and thermal
fields at Pr≤1, it is not totally necessary to employ the correct near-wall variation
ofturbulent viscosity.) Forrough wallcases, itis confirmed thatthemodel function
of Pr
t
inside roughness elements enables theAWF to perform well in high Pr flows
at least at Pr≤10.
With a slight modification, the AWF can reproduce the characteristics of the
turbulence near free surfaces.The predictive performance of such a version of the
AWF isreasonable inturbulent concentration fieldsin the rangeof Sc=1 to1,000.
Acknowledgements
The author thanks Professors B. E. Launder, H. Iacovides and Dr.T. J. Craft of the
Universityof Manchesterfortheirfruitfuldiscussions andcommentsontheAWFs.
AppendixA
The analytical integration of the momentum and energy equations (17) and (18) is
performed in the four different cases illustrated in figure 9.8. The process for the
case (a) y
v
< 0 is as follows:
The integration of equation (17) with equation (40) is:
If y
∗
≤ h
∗
,
dU
dy
∗
=
A
U
µ{1 +α(y
∗
− y
∗
v
)}
=
A
U
µY
∗
(A.1)
U =
A
U
αµ
lnY
∗
+ B
U
(A.2)
At a wall: y
∗
=0, the condition U =0 leads to:
B
U
=−
A
U
αµ
ln(1 − αy
∗
v
) =−
A
U
αµ
lnY
∗
w
(A.3)
When h
∗
< y
∗
, the integration leads to:
dU
dy
∗
=
C
U
y
∗
+ A
U
µY
∗
(A.4)