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-   -   Shear stress in perforated pipe for horizontal wells (http://www.cfd-online.com/Forums/cfx/108037-shear-stress-perforated-pipe-horizontal-wells.html)

mohw2002 October 12, 2012 17:24

Shear stress in perforated pipe for horizontal wells
 
I am working on the wellbore (perforated pipe) for horizontal wells. I want to calculate the shear stress tau w and friction factor f from CFX.

sakurabogoda October 13, 2012 03:27

As far as I know, it is not easy to find friction factor by CFX as when you model it you should input stream-wise and transverse loss coefficients. Without knowing them you cannot model it. So better to do a simulation or get experimental data.
Pls. this is according to my knowledge and experiences. :)

ghorrocks October 13, 2012 05:32

What friction factor are you looking for? There are many definitions of it.

Wall shear stress is easy to extract - is this what you mean by shear stress tau w?

mohw2002 October 13, 2012 10:28

Hi ghorrocks.
I mean how can I calculate the shear stress inside the pipe wall due pressure drop due to wall friction and then calculate friction factor f for turbulent flow. I am using CFX k-epsilon model.

Regards.

mohw2002 October 13, 2012 10:31

Hi Sakurabogoda.
How can I input stream-wise and transverse loss coefficients.

Regards.

ghorrocks October 14, 2012 04:13

Getting the wall shear stress is simple, it is a variable in the results file by default. Then you just need to get an average of it at the representative point along the length, and you can get the pressure drop from that. This is all pretty standard post-processing.

Sorry, what is stream wise and transverse loss coefficients? How are you defining these terms?

sakurabogoda October 15, 2012 00:54

When you do a porous or perforated design, you have to input directional losses; streamwise and transverse. Both are related to pressure drop and transverse loss can be take in terms of Streamwise coefficient. That is why I told to do simulation or experiment, to get pressure drop.

Dear Glenn,
I am doubt about how to get pressure drop by CFX without knowing directional losses. I would really appreciate your advice.

mohw2002 October 15, 2012 02:52

Quote:

Originally Posted by sakurabogoda (Post 386598)
When you do a porous or perforated design, you have to input directional losses; streamwise and transverse. Both are related to pressure drop and transverse loss can be take in terms of Streamwise coefficient. That is why I told to do simulation or experiment, to get pressure drop.

Dear Glenn,
I am doubt about how to get pressure drop by CFX without knowing directional losses. I would really appreciate your advice.

Dear sakura
Sorry how can I do to input directional losses; streamwise and trasverse by CFX? I mean where? do you have toturial about this?

sakurabogoda October 15, 2012 04:20

Dear Mohammed,
Refer "Flow in a Catalytic Converter" in tutorial manual. It is about a porous domain, but you can get an idea how to modify it into your model. :)

ghorrocks October 15, 2012 05:22

Assuming you have a normal fluid domain (not a porous domain) then can't you simply put a series of points (or maybe a line) along the centre line of the pipe and monitor points at the periphery? Then your streamwise loss coefficient can be calculated from the pressure drop along the pipe, and the transverse loss can be calculated from the pressure drop from inside the pipe to outside?

This is just straight forward post-processing.

mohw2002 October 19, 2012 16:58

Quote:

Originally Posted by ghorrocks (Post 386632)
Assuming you have a normal fluid domain (not a porous domain) then can't you simply put a series of points (or maybe a line) along the centre line of the pipe and monitor points at the periphery? Then your streamwise loss coefficient can be calculated from the pressure drop along the pipe, and the transverse loss can be calculated from the pressure drop from inside the pipe to outside?

This is just straight forward post-processing.

Hi
How can I do it at the post-processing without fix it at pre-processing?

mohw2002 October 19, 2012 17:06

Quote:

Originally Posted by sakurabogoda (Post 386625)
Dear Mohammed,
Refer "Flow in a Catalytic Converter" in tutorial manual. It is about a porous domain, but you can get an idea how to modify it into your model. :)

Dear
When I consider my geometry (perforated pipe) as a Catalytic Converter I have some questions
1- There is domain named (Subtarte) but how can I put in my model like that.
2- How much the value of volume porosity?
3- Set streamwise loss which one I will choose?
4- Can I use the Quadratic Resistance coefficient or another one?
5- How much value use to the streamwise coefficient Multiplier?
thanks

ghorrocks October 20, 2012 05:20

Quote:

How can I do it at the post-processing without fix it at pre-processing?
This is basic post-processing. Have you done the CFX tutorials? They describe how to post process your results. Likewise your reply to Mohammed is basic CFD which is covered in the tutorials.

sakurabogoda October 21, 2012 21:16

Dear Mohammed,
All parameters depend on your design. Read CFX theory guide and there it specified how to create the domain and loss model, with/without the effect of volume porosity.
Other setting has to be define by you. You should have a stramwise loss due to the wall shear.


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