
[Sponsors] 
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: 5 
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: 6 
As far as I know, it is not easy to find friction factor by CFX as when you model it you should input streamwise 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: 12,397
Rep Power: 96 
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: 5 
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 kepsilon model. Regards. 

October 13, 2012, 10:31 

#5 
New Member
Mohammed
Join Date: Oct 2012
Posts: 27
Rep Power: 5 
Hi Sakurabogoda.
How can I input streamwise and transverse loss coefficients. Regards. 

October 14, 2012, 04:13 

#6 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,397
Rep Power: 96 
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 postprocessing.
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: 6 
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: 5 
Quote:
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: 6 
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: 12,397
Rep Power: 96 
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 postprocessing. 

October 19, 2012, 16:58 

#11  
New Member
Mohammed
Join Date: Oct 2012
Posts: 27
Rep Power: 5 
Quote:
How can I do it at the postprocessing without fix it at preprocessing? 

October 19, 2012, 17:06 

#12  
New Member
Mohammed
Join Date: Oct 2012
Posts: 27
Rep Power: 5 
Quote:
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
Posts: 12,397
Rep Power: 96 
Quote:


October 21, 2012, 21:16 

#14 
Senior Member
S.Bogoda
Join Date: Jul 2012
Posts: 133
Rep Power: 6 
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. 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Measuring wall shear stress in bend pipe  liguifan  OpenFOAM  70  December 9, 2015 04:49 
Wall Shear Stress in a Pipe  itsme_kit  CDadapco  4  February 11, 2012 13:32 
shear stress scalar definitions?  Novak Elliott  CFX  0  April 6, 2003 01:45 
Terrible Mistake In Fluid Dynamics History  Abhi  Main CFD Forum  12  July 8, 2002 09:11 
What is the detail definition of wall shear stress  zjm  FLUENT  0  January 2, 2002 08:43 