CFD Online Discussion Forums

CFD Online Discussion Forums (
-   CFX (
-   -   Porous Help (

shaswat February 24, 2012 01:13

Porous Help
1 Attachment(s)
Dear friends

I am doing fluid flow through multilayer artery porous wall. The wall layers are in micrometer.

I would like to define porosity and permeability of the layers

The length of wall 120mm
thickness of the wall layer is 0.5mm
I have four layers thickness starts from 2micro meter, 10 micrometer, 2 micrometer, 400 micrometer and so on.

Flow is in the Z direction.

when r=0 , it is the axis of the tube.
The fluid domain diameter 2.5 mm

Please clarify my doubts

1. I defined

porosity and permiabilty as function of radius . Is it correct?

2. I use one dimensional function as shown below

radius (mm) ---------------------------- porosity
1.25001 ------------------------------- 0.005
1.25002 ----------------- --------------- 0.005
1.6001 --------------- ------------- 0.02
1.6002--------------- ---------- 0.02

and so on

I check the the box
extened min
extended max

Is the above correct? or should I remove the extended min / extended max?
What is the porosity value at the interface at r=1.25mm?

If I check the box extended min, it will be in the fluid domain.
Please help me , How can I handle this?



ghorrocks February 24, 2012 07:19

Have you considered the implications of what you are doing? You have layer thicknesses of 2, 10, 2, 400 microns. Why model the 2 and 10 micron layers? Do they add anything significant? If they are significant, then why not just model the 400 micron layer and combine all the 2 and 10 micron layers into a flow resistance at the inside of the 400 micron layer?

To get your model to model the 2 micron layer you are going to need an element of at most 2um, more like 1um to be sure just ensure you resolve the thin layer. That mean you need approximately 250 elements through the thickness. Do you have enough computing power to run a model with this many elements?

shaswat February 24, 2012 09:42

Dear friend

I am not going to use layer by layer. I use only the porosity as a function of radius
is it possible in the 2micro meter and 10 micrometer thickness?



ghorrocks February 25, 2012 06:49

I do not understand your last comment.

Simply put, to resolve a 2um thick porous region you need a mesh smaller than 2um. That will probably lead to a massive mesh, or huge aspect ratio changes.

All times are GMT -4. The time now is 21:46.