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

restarting paused transient simulation using reactingFoam

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 6, 2015, 14:15
Default restarting paused transient simulation using reactingFoam
  #1
New Member
 
Josh Dawson
Join Date: Oct 2014
Location: Justin, TX
Posts: 19
Rep Power: 8
JMDag2004 is on a distinguished road
Something strange happened when I restarted a simulation while using reactingFoam. I don't believe it had anything to do with the solver being used as I understand "time-step continuity errors" are more relevant to the PISO algorithm. I am building a combustion simulation and everything was running perfect. The simulation has a rather refined mesh and due to the nature of the simulation I have to maintain a very small time step CFL < 0.1. This obviously necessitates parallel processing. When I complete a quality simulation I will eventually need to run a mesh convergence study, which will take the needed computing resources beyond my laptop. The next step will be to use a high powered computing center, TACC if you are familiar. I have a hyperthreaded quad core and run in parallel using 8 processors. After running for 8 hours I decided to give my laptop a break and used the "writeNow" functionality looking to pick up the simulation the following day. Before stopping the simulation,the time step errs were extremely low. The overall err was on the order of 10^-11, residuals looked good, temp/pressure/vel/enthalpy/specie mass fractions all looked good before stopping the simulation. Upon restart, the overall time step err jumped to roughly 0.01 while flow variables looked the same. After two more hours or so the min temp dropped to 200 without tripping the janaf temp warning. I wanted to see if anyone had experienced anything like this before because I will almost assuredly have to stop and start the simulation multiple times using TACC time allocation and wanted to see if there is something I might be able to do to prevent these problems from happening again. I stopped the simulation again because I haven't been able to look closely at flow variables after the temp dropped to see what kind of impact this has had.
JMDag2004 is offline   Reply With Quote

Old   August 10, 2015, 11:15
Default
  #2
Member
 
Howar
Join Date: Mar 2015
Posts: 53
Rep Power: 7
Howard is on a distinguished road
Quote:
Originally Posted by JMDag2004 View Post
Something strange happened when I restarted a simulation while using reactingFoam. I don't believe it had anything to do with the solver being used as I understand "time-step continuity errors" are more relevant to the PISO algorithm. I am building a combustion simulation and everything was running perfect. The simulation has a rather refined mesh and due to the nature of the simulation I have to maintain a very small time step CFL < 0.1. This obviously necessitates parallel processing. When I complete a quality simulation I will eventually need to run a mesh convergence study, which will take the needed computing resources beyond my laptop. The next step will be to use a high powered computing center, TACC if you are familiar. I have a hyperthreaded quad core and run in parallel using 8 processors. After running for 8 hours I decided to give my laptop a break and used the "writeNow" functionality looking to pick up the simulation the following day. Before stopping the simulation,the time step errs were extremely low. The overall err was on the order of 10^-11, residuals looked good, temp/pressure/vel/enthalpy/specie mass fractions all looked good before stopping the simulation. Upon restart, the overall time step err jumped to roughly 0.01 while flow variables looked the same. After two more hours or so the min temp dropped to 200 without tripping the janaf temp warning. I wanted to see if anyone had experienced anything like this before because I will almost assuredly have to stop and start the simulation multiple times using TACC time allocation and wanted to see if there is something I might be able to do to prevent these problems from happening again. I stopped the simulation again because I haven't been able to look closely at flow variables after the temp dropped to see what kind of impact this has had.
Have u solved the problem?
Howard is offline   Reply With Quote

Reply

Tags
janaf, parallel, reactingfoam, time step continuity, writenow

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
Question on transient simulation in OpenFOAM and FLUENT nicklj OpenFOAM Running, Solving & CFD 4 May 8, 2014 23:30
Exporting data of transient simulation DURING a simulation, at user locations ? Milan2013 CFX 0 April 18, 2014 04:47
the problem of my transient simulation "Floating point exception: Overflow " alloveyou CFX 15 November 22, 2012 12:14
Beginning a Transient Simulation Norflow CFX 2 October 7, 2011 01:38
Resume Transient simulation HMR CFX 1 June 28, 2011 22:13


All times are GMT -4. The time now is 16:36.