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

The effects of BCs and the initial conditions on the final results

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

Like Tree1Likes
  • 1 Post By duri

Reply
 
LinkBack Thread Tools Display Modes
Old   August 27, 2013, 22:31
Default The effects of BCs and the initial conditions on the final results
  #1
New Member
 
mj
Join Date: Apr 2011
Posts: 24
Rep Power: 6
mrji8011 is on a distinguished road
Dear Friends
Does anyone know any paper which investigated the boundary conditions or initial condition effects on final results of two phase flow simulation?
I have simulated ship motion and its wave propagation by Fluent software with different BCs (velocity inlet or pressure inlet) and initial conditions (zero velocity or equal inlet velocity). The results of the simulations are completely different. In addition I did simulate by MRF approach and stationary, again the results are different.
Thanks for your help in advance
mrji8011 is offline   Reply With Quote

Old   August 28, 2013, 00:46
Default
  #2
Member
 
aerosjc
Join Date: Aug 2012
Posts: 32
Rep Power: 4
aerosjc is on a distinguished road
based on theoretical knowledge of your focused problem, you can select suitable BC. I never saw any papers on this kind of research. So, maybe to take time to study theoretical knowledge is what you should do. My advice.
aerosjc is offline   Reply With Quote

Old   August 28, 2013, 03:53
Default
  #3
Senior Member
 
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,587
Rep Power: 20
FMDenaro will become famous soon enough
...but theoretically I see correct that different BC and initial conditions drive to different solutions
FMDenaro is offline   Reply With Quote

Old   August 28, 2013, 08:37
Default
  #4
Member
 
Join Date: Jul 2013
Posts: 37
Rep Power: 3
Alex C. is on a distinguished road
Assuming the uniqueness of the steady-state solution for 3d N-S (which there is no proof for that fact to be true...) the initial condition should not have an influence on the steady-solution. That being said, the transient domain will obviously be altered by a different initial condition.

In my opinion, there is no reason to think different boundary conditions will lead to the same solution, unless you specify an equivalent boundary. As exemple : after running a velocity inlet solution, you could export the pressure field on the inlet, and specify a pressure inlet with that pressure field, which should therefore lead to the same solution.
Alex C. is offline   Reply With Quote

Old   August 28, 2013, 10:39
Default
  #5
Senior Member
 
duri
Join Date: May 2010
Posts: 130
Rep Power: 7
duri is on a distinguished road
Quote:
Originally Posted by mrji8011 View Post
I have simulated ship motion and its wave propagation by Fluent software with different BCs (velocity inlet or pressure inlet) and initial conditions (zero velocity or equal inlet velocity).
Velocity inlet BC and pressure inlet BC are different in fluent, it preserves velocity and total pressure respectively. So difference in results are expected.
Initial condition will not lead to different solution. But the path of convergence will get affected. Probably one of the conditions is not properly converged. (For convergence, don't just go by residual, some times residual settle faster than the flow quantities)
aerosjc likes this.
duri is offline   Reply With Quote

Reply

Tags
boundary condition, initial condition, multi reference frams

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



All times are GMT -4. The time now is 02:56.