Position Dependent Porous Media
The domain is divided into two fluid zones. In the fluid-2 cell zone, an X-momentum source
term is included for each cell using UDF. This source term models the effect of a porous
plug on the flow in the X-direction and is given by:
S
x
= −
1
2
Cρy|u|u (1)
where C = 100 is a model constant.
Equation source terms are added using the DEFINE SOURCE macro.
The finite-volume solver of ANSYS FLUENT expects the source term to be linearized ac-
cording to the following convention:
S
φ
= A + Bφ =
S
∗
−
∂S
φ
∂φ
∗
φ
∗
| {z }
A
+
∂S
φ
∂φ
∗
| {z }
B
φ (2)
where the superscript ∗ represents the value at the previous iteration. B (called dS[eqn]
in the UDF macro) can be coded explicitly by using currently known value of φ, and the
entire S is returned by DEFINE SOURCE. For the simple source of X-momentum equation in
this problem,
B =
∂S
x
∂u
= −Cρy|u|. (3)
For more details, examine the source code (porous plug.c) as shown in the Appendix.
Setup and Solution
Preparation
1. Copy the files (porous plug.msh and porous plug.c) to your working folder.
2. Use FLUENT Launcher to start the 2D version of ANSYS FLUENT.
For more information about FLUENT Launcher see Section 1.1.2, Starting
ANSYS FLUENT Using FLUENT Launcher in ANSYS FLUENT 12.0 User’s Guide.
3. Enable Double-Precision in the Options list.
4. Click the UDF Compiler tab and ensure that the Setup Compilation Environment for
UDF is enabled.
The path to the .bat file which is required to compile the UDF will be displayed as soon
as you enable Setup Compilation Environment for UDF.
If the UDF Compiler tab does not appear in the FLUENT Launcher dialog box by default,
click the Show More >> button to view the additional settings.
The Display Options are enabled by default. Therefore, after you read in the mesh, it
will be displayed in the embedded graphics window.
2
c
ANSYS, Inc. September 17, 2009
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