# Shear stress in perforated pipe for horizontal wells

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 October 12, 2012, 17:24 Shear stress in perforated pipe for horizontal wells #1 New Member   Mohammed Join Date: Oct 2012 Posts: 27 Rep Power: 4 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.

 October 13, 2012, 03:27 #2 Senior Member   S.Bogoda Join Date: Jul 2012 Posts: 133 Rep Power: 5 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.

 October 13, 2012, 05:32 #3 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,821 Rep Power: 85 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?

 October 13, 2012, 10:28 #4 New Member   Mohammed Join Date: Oct 2012 Posts: 27 Rep Power: 4 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.

 October 13, 2012, 10:31 #5 New Member   Mohammed Join Date: Oct 2012 Posts: 27 Rep Power: 4 Hi Sakurabogoda. How can I input stream-wise and transverse loss coefficients. Regards.

 October 14, 2012, 04:13 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,821 Rep Power: 85 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?

 October 15, 2012, 00:54 #7 Senior Member   S.Bogoda Join Date: Jul 2012 Posts: 133 Rep Power: 5 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.

October 15, 2012, 02:52
#8
New Member

Mohammed
Join Date: Oct 2012
Posts: 27
Rep Power: 4
Quote:
 Originally Posted by sakurabogoda 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?

 October 15, 2012, 04:20 #9 Senior Member   S.Bogoda Join Date: Jul 2012 Posts: 133 Rep Power: 5 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.

 October 15, 2012, 05:22 #10 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,821 Rep Power: 85 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.

October 19, 2012, 16:58
#11
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Mohammed
Join Date: Oct 2012
Posts: 27
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Quote:
 Originally Posted by ghorrocks 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?

October 19, 2012, 17:06
#12
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Mohammed
Join Date: Oct 2012
Posts: 27
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Quote:
 Originally Posted by sakurabogoda 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

October 20, 2012, 05:20
#13
Super Moderator

Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
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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.

 October 21, 2012, 21:16 #14 Senior Member   S.Bogoda Join Date: Jul 2012 Posts: 133 Rep Power: 5 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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