CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

momentum loss

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree2Likes
  • 1 Post By banty
  • 1 Post By kingjewel1

Reply
 
LinkBack Thread Tools Display Modes
Old   April 7, 2012, 11:06
Default momentum loss
  #1
New Member
 
suong
Join Date: Apr 2012
Posts: 7
Rep Power: 5
congsu is on a distinguished road
hi
Can someone tell me:
how to calculate energy or momentum of fluid loss behind the cylinders. ( flow past the cylinder)
thank so much!
congsu is offline   Reply With Quote

Old   April 7, 2012, 16:19
Default
  #2
Member
 
banty
Join Date: Mar 2012
Posts: 52
Rep Power: 5
banty is on a distinguished road
Hi,
U can write a UDF for energy calculation at particular time
E = (rho* Velocity*Velocity)/2
congsu likes this.
banty is offline   Reply With Quote

Old   April 8, 2012, 10:18
Default
  #3
New Member
 
suong
Join Date: Apr 2012
Posts: 7
Rep Power: 5
congsu is on a distinguished road
Thank a lot, and I think i must spent more time to learn UDF. i'm a beginner
congsu is offline   Reply With Quote

Old   April 8, 2012, 13:16
Default
  #4
Senior Member
 
Join Date: Jul 2009
Posts: 211
Rep Power: 9
kingjewel1 is on a distinguished road
Quote:
Originally Posted by congsu View Post
Thank a lot, and I think i must spent more time to learn UDF. i'm a beginner
  • You don't need a UDF for such a simple thing. Use a Custom Defined Function. It's like a calculator with all the different variables.
  • Alternatively you can open your solved case into CFDpost and use a CEL function like
  • ave(u-velocity^2)@point behind cylinder/2*rho

That's not the exact command because you have to define that point in either Fluent or in CFD post.

If you want to calculate the average momentum or energy in a volume, you need to cut that volume out of the domain. If that's what you want to do, I'll help further.
congsu likes this.
kingjewel1 is offline   Reply With Quote

Old   April 8, 2012, 22:49
Default
  #5
New Member
 
suong
Join Date: Apr 2012
Posts: 7
Rep Power: 5
congsu is on a distinguished road
Quote:
Originally Posted by kingjewel1 View Post
If you want to calculate the average momentum or energy in a volume, you need to cut that volume out of the domain. If that's what you want to do, I'll help further.
Thank a lot kingjewel1. Yes, i want to calculate the average momentum or energy . Can use help me how to cut that volume out of the domain and how to calculate it, more detail, please..
congsu is offline   Reply With Quote

Old   April 9, 2012, 05:25
Default
  #6
Senior Member
 
Join Date: Jul 2009
Posts: 211
Rep Power: 9
kingjewel1 is on a distinguished road
When you say you want to calculate the average momentum loss behind a cylinder what exactly do you mean? can you draw it for us?

Is it the momentum you want to calculate in a given volume behind the cylinder?

If that's the case what you need to do is decide what size this volume needs to be and the bounding coordinates (x0 y0 z0) and (x1 y1 z1).
Go to Adapt -Region - Put in those coordinate and click MARK.
Then go to Mesh -Separate- Zones choose the two fluid zones you want to split and that's your volume created. It's still perfectly transparent to the fluid, just has a separate name.

Then go to Report/Volume/Volume-Average choose which volume you want to calculate in (ie your new one) and then choose your variable. Since you have a particular equation, you need to define this first in Custom Field Functions for it to appear in the list available in report.

You can also set this as a volume monitor during calculation eg for a convergence criterium.

Hope that helps.
kingjewel1 is offline   Reply With Quote

Old   April 11, 2012, 07:55
Default
  #7
New Member
 
suong
Join Date: Apr 2012
Posts: 7
Rep Power: 5
congsu is on a distinguished road
thank you for replying
it is very useful.
I did it.
congsu is offline   Reply With Quote

Reply

Thread Tools
Display Modes

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 Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
momentum loss equation porous media pato CFX 1 March 21, 2012 19:28
Momentum source / porous loss ijk CFX 5 May 20, 2011 10:30
Derivation of Momentum Equation in Integral Form Demonwolf Main CFD Forum 2 October 29, 2009 20:53
2D momentum source for pressure loss Bernhard Dobmeier CFX 0 December 5, 2006 05:05
Experts in momentum loss please help jemteo CFX 7 March 15, 2006 23:42


All times are GMT -4. The time now is 08:06.