# Friction Factor Calculation in Pipe

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

June 13, 2011, 06:40
Friction Factor Calculation in Pipe
#1
Senior Member

Morteza
Join Date: May 2010
Location: Iran,Islamic Republic of
Posts: 161
Rep Power: 9
Dear Friends

I have modelled a 3d pipe in Gambit and Fluent.
To validate the results I have to calculate the friction factor in the pipe.
There are so many threads in cfd-online , but there is not any satisfying response.
I read in a tutorial that I have to calculate the friction factor using the below formula:

f=(8*shear stress)/(density* average velocity^2)

But, the question is here, how can I calculate the mean velocity?
in which plane i have to calculate that?
and how to calculate the shear stress?

the pipe diameter : 0.12m
velocity : 12.17 m/s along negative z

thank you in advance
Morteza

If you like send you the full version of the attached pdf, please write your emails down.
Attached Files
 pipe.pdf (58.8 KB, 225 views)

 June 13, 2011, 07:19 #2 Member     Join Date: Mar 2009 Posts: 72 Rep Power: 10 The file you attached answers all your questions as far as I see it. It describes how to calculate mean velocity and the shear stress as well as in which plane you are supposed to calculate them. Are there any hidden problems in your questions that I missed? __________________ "Trying is the first step to failure." - Homer Simpson

June 13, 2011, 07:31
#3
Senior Member

Morteza
Join Date: May 2010
Location: Iran,Islamic Republic of
Posts: 161
Rep Power: 9
Quote:
 Originally Posted by Ford Prefect The file you attached answers all your questions as far as I see it. It describes how to calculate mean velocity and the shear stress as well as in which plane you are supposed to calculate them. Are there any hidden problems in your questions that I missed?

Dear Ford Perfect
showed in the file that I must create an ISOSURFACE for calculating the mean velocity and stress.
I found that tutorials creat the surface in the last section of the pipe(exit plane)... but I am puzzled in assigning an ISO-value for this surface. as well, I think the tutorials chose the z-cordinate according its own model.
In what coordinate i have to create the iso surface?
my inlet plane and exit plane are located in xy . and the axis of the pipe is along the negative z axis. from (0,0,0) to (0,0,-0.12)
reynolds number: 100000
diameter: 0.12
inlet velocity: 12.17 m/s

 June 13, 2011, 07:46 #4 Member     Join Date: Mar 2009 Posts: 72 Rep Power: 10 Just "surface > iso surface" then pick surface of constant "mesh > z-coordinate" assuming that z-coordinate is in the axial direction. Then you have to choose where you wish to create the surface along the axis. If you like you can also pick the outlet surface directly since that is already present in your model. __________________ "Trying is the first step to failure." - Homer Simpson

June 14, 2011, 14:41
#5
Senior Member

Morteza
Join Date: May 2010
Location: Iran,Islamic Republic of
Posts: 161
Rep Power: 9
Quote:
 Originally Posted by Ford Prefect Just "surface > iso surface" then pick surface of constant "mesh > z-coordinate" assuming that z-coordinate is in the axial direction. Then you have to choose where you wish to create the surface along the axis. If you like you can also pick the outlet surface directly since that is already present in your model.
Dear friend
I did all according the file.
I created an ISO-SURFACE at the outlet plane of the pipe....
I calculated the shear stress on the wall as the tutorial did.
and also the average velocity.
but I think the calculated value of friction factor is wrong.
It is something two times more than the value of moody diagram.

the tutorial has modeled half of a pipe.
But i modeled the entire pipe.
Isn't it the reason for non-satisfying value of friction factor???

 June 2, 2016, 16:35 tutorial #6 New Member   moenas Join Date: Jan 2016 Posts: 13 Rep Power: 4 can you send me the tutorial m.nasser@zu.edu.eg

 June 27, 2016, 09:05 #7 New Member   fahimeh Join Date: May 2016 Location: Tehran, Iran Posts: 9 Rep Power: 3 I have the same problem. I would be grateful if you send me the tutorial. F.khanmohammadi@stu.nit.ac.ir

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post [DesignModeler] DesignModeler Pipe within pipe shields ANSYS Meshing & Geometry 12 April 30, 2015 03:58 beginner FLUENT 1 July 30, 2007 15:16 Abhi Main CFD Forum 2 July 9, 2002 09:08 Abhi Main CFD Forum 12 July 8, 2002 09:11 ram Main CFD Forum 5 June 17, 2000 21:31

All times are GMT -4. The time now is 19:00.

 Contact Us - CFD Online - Privacy Statement - Top