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

Time Step decreases after a long time of running, why?

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

Like Tree1Likes
  • 1 Post By Krao

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 14, 2019, 06:48
Smile Time Step decreases after a long time of running, why?
  #1
New Member
 
Nidal
Join Date: Nov 2018
Posts: 5
Rep Power: 4
Nidalsb is on a distinguished road
Hi,

My time step starts out at ~1e-9 which is acceptable since my model is basically a 2mm block. After many time steps, almost 1500, my time step decreases to ~1e-15. Anyone knows the reason why this might happen?

Thanks a lot
Nidalsb is offline   Reply With Quote

Old   October 14, 2019, 07:33
Default
  #2
Senior Member
 
Kmeti Rao
Join Date: May 2019
Posts: 145
Rep Power: 4
Krao is on a distinguished road
Which simulation you are using? What kind of solver?
Please go through the following link.
How to give enough info to get help

Assuming that you are using a transient solver, check your CFL(courant number), also, the solver settings and quality of the mesh you are using. If something is not ok please fix it
Krao is offline   Reply With Quote

Old   October 14, 2019, 07:40
Default
  #3
New Member
 
Nidal
Join Date: Nov 2018
Posts: 5
Rep Power: 4
Nidalsb is on a distinguished road
I am using rhoPimpleFoam, When I did the simulation using first order divergence schemes it worked just fine. now that I am solving using second order the time step reduces a lot after some time steps. basically my simulation is a pressure difference across porous media. I have a geometry of a porous structure and I am simulating flow across it. Please let me know if you need more info. My courant number is set to a max of 1, even if I increase it to 5 the time step remains ~1e-15
Nidalsb is offline   Reply With Quote

Old   October 15, 2019, 03:40
Default
  #4
Senior Member
 
Kmeti Rao
Join Date: May 2019
Posts: 145
Rep Power: 4
Krao is on a distinguished road
I have not carried out simulations in your application but during dynamic simulation of external flow over a propeller, I had similar issues. I have overcome that by improving the quality of mesh and calculating the possible time step using CFL.
MaySea likes this.
Krao is offline   Reply With Quote

Old   October 26, 2020, 06:33
Default
  #5
New Member
 
Join Date: Nov 2018
Posts: 28
Rep Power: 4
MaySea is on a distinguished road
Hi Kmeti,

May I ask you how exactly did you improve the mesh quality? Did you decrease non-orthogonality?

Cheers,
Jan
MaySea 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
AMI speed performance danny123 OpenFOAM 21 October 24, 2020 05:13
courant number increases to rather large values 6863523 OpenFOAM Running, Solving & CFD 21 November 10, 2019 11:14
High Courant Number @ icoFoam Artex85 OpenFOAM Running, Solving & CFD 11 February 16, 2017 14:40
mixerVesselAMI2D's mass is not balancing sharonyue OpenFOAM Running, Solving & CFD 6 June 10, 2013 10:34
Upgraded from Karmic Koala 9.10 to Lucid Lynx10.04.3 bookie56 OpenFOAM Installation 8 August 13, 2011 05:03


All times are GMT -4. The time now is 23:52.