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

solids4foam_strange solid behaviour

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

Like Tree1Likes
  • 1 Post By bigphil

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 18, 2022, 11:28
Smile solids4foam_strange solid behaviour
  #1
New Member
 
Tommaso
Join Date: Jan 2020
Posts: 16
Rep Power: 6
evxta3 is on a distinguished road
Hi all, I am modelling a solitary wave impacting a flexible plate with solids4foam. The plate shows a strange beahviour, such as the horizontal displacement is constant over certain times (as in the attached Fig. 1). The force acting on the plate due to the wave is shown in Fig. 2.

It seems that the solid is not updated over those time steps.

Any idea about why this is happening?

Thanks,
Tommaso
Attached Images
File Type: png Fig. 1.png (15.8 KB, 12 views)
File Type: png Fig. 2.png (15.6 KB, 10 views)

Last edited by evxta3; October 26, 2022 at 04:18.
evxta3 is offline   Reply With Quote

Old   November 25, 2022, 12:04
Default
  #2
Super Moderator
 
bigphil's Avatar
 
Philip Cardiff
Join Date: Mar 2009
Location: Dublin, Ireland
Posts: 1,089
Rep Power: 34
bigphil will become famous soon enoughbigphil will become famous soon enough
Hi Tommaso,

Can you give more details of your case? For example, the geometry, materials and loading conditions.

Philip
bigphil is offline   Reply With Quote

Old   December 13, 2022, 10:48
Default
  #3
New Member
 
Tommaso
Join Date: Jan 2020
Posts: 16
Rep Power: 6
evxta3 is on a distinguished road
Hi Philip, thanks for your reply. This was a 2d wave flume with a rectangular plate. The plate material was stainless steel (density: 8000 kg/m^3 and Young's modulus 200 GPa). The plate, partially submerged, was impacted by a solitary wave resulting in the total force shown in the figure in my previous post.

Thanks,
Tommaso
evxta3 is offline   Reply With Quote

Old   December 14, 2022, 10:11
Default
  #4
Super Moderator
 
bigphil's Avatar
 
Philip Cardiff
Join Date: Mar 2009
Location: Dublin, Ireland
Posts: 1,089
Rep Power: 34
bigphil will become famous soon enoughbigphil will become famous soon enough
What are the boundary conditions on the plate?

And what does the log file look like for the time steps where the displacement stays constant?
bigphil is offline   Reply With Quote

Old   December 14, 2022, 10:36
Default
  #5
New Member
 
Tommaso
Join Date: Jan 2020
Posts: 16
Rep Power: 6
evxta3 is on a distinguished road
The plate is fixed at the bottom

{
type fixedDisplacement;
value uniform (0 0 0);
}


and the remaining boundaries are treated as interface with

{
type solidTraction;
traction uniform ( 0 0 0 );
pressure uniform 0;
value uniform (0 0 0);
}


From the log file it looks like that the plate is not updated at all since the resisuals converged during the time steps where the displacement is constant. Something like that:

PIMPLE: converged in 2 iterations
Setting traction on solid patch
Interpolating from fluid to solid using GGI/AMI interpolation
Total force (fluid) = (-1.30659 -0.787151 -0.926353)
Total force (solid) = (1.30662 0.78712 0.926346)
Evolving solid solver
Solving the momentum equation for D
Corr, res, relRes, matRes, iters
The relative residual has converged
2, 9.99787e-07, 0, 0, 0


If I use a much thicker plate (more cells through the plate thickness) this strange behaviour is not observed anymore.

Thanks,
Tommaso
evxta3 is offline   Reply With Quote

Old   December 21, 2022, 10:58
Default
  #6
Super Moderator
 
bigphil's Avatar
 
Philip Cardiff
Join Date: Mar 2009
Location: Dublin, Ireland
Posts: 1,089
Rep Power: 34
bigphil will become famous soon enoughbigphil will become famous soon enough
For the thinner plate, I suspect that the solid solver prematurely converges in some time steps, which means the displacement stays constant in these steps. You could check if tightening the solution tolerances in constant/solidProperties helps.
evxta3 likes this.
bigphil is offline   Reply With Quote

Old   December 21, 2022, 11:19
Default
  #7
New Member
 
Tommaso
Join Date: Jan 2020
Posts: 16
Rep Power: 6
evxta3 is on a distinguished road
Quote:
Originally Posted by bigphil View Post
For the thinner plate, I suspect that the solid solver prematurely converges in some time steps, which means the displacement stays constant in these steps. You could check if tightening the solution tolerances in constant/solidProperties helps.
Yes, that helps in some cases (not always though). Thanks Philip!
evxta3 is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Solid combustion problem.... godspeedsam FLUENT 3 May 24, 2022 04:29
Question about heat transfer coefficient setting for CFX Anna Tian CFX 1 June 16, 2013 06:28
Error finding variable "THERMX" sunilpatil CFX 8 April 26, 2013 07:00
Moving solid problem Mudblood FLUENT 0 June 10, 2010 12:11
How to calculate density of solid phase zhou Main CFD Forum 0 December 17, 1999 19:06


All times are GMT -4. The time now is 06:57.