CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

how to treat the stiff source terms in reacting flows

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

LinkBack Thread Tools Display Modes
Old   March 31, 2015, 22:47
Default how to treat the stiff source terms in reacting flows
New Member
Join Date: Mar 2015
Posts: 10
Rep Power: 2
dli is on a distinguished road
Hi guys,
I am writing a code to simulate the detonation ,but I don't have any efficient method to treat those stiff source terms. The subcycle in the global timestep was used ,but it's only 1-order,it's not very accurate in the unsteady flow.I also read some papers about the linearly point implicit method which avoid the stiff source problem,but it's very difficult to derive the source Jacobi matrix,and it's different from the mechanisms, so I want to get the Jacobi matrix by the standard different quotients,is it appropriate to get Jacobi matrix from this method?(may it is a little time-consuming to do this,but i think it's general for many mechanisms)

so ,any one can give me help or give me some suggestions about this?
dli is offline   Reply With Quote

Old   April 1, 2015, 00:47
Senior Member
Michael Prinkey
Join Date: Mar 2009
Location: Pittsburgh PA
Posts: 141
Rep Power: 12
mprinkey will become famous soon enough
In my experience, stiff chemistry is usually handled via time splitting. You solve the species transport equations ignoring the reaction terms and using (say) an implicit scheme and timestep based on flow behavior. Then you treat each finite volume as a fixed volume reactor and use a stiff solver (like CVODE) to integrate the reactions in each cell using adaptive (sub) timestepping up to the new flow time--the chemical composition is over written from the previous timestep. ISAT/DOLFA can be inserted ahead of CVODE to tabulate and interpolate stiff chemistry integrations and speed overall computation speed.

Note that they computational time from cell-to-cell and from timestep-to-timestep can vary wildly as CVODE steps carefully through the rapid reactions (I've seen 10^-9 sec timesteps!). If you are running this on one CPU, this isn't a big deal, but for OpenMP and/or MPI implementations, this can wreak havoc with parallel load balancing.
mprinkey is offline   Reply With Quote

Old   April 1, 2015, 04:34
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,780
Rep Power: 23
FMDenaro will become famous soon enough
I remember some published studies of LeVeque about numerical treatment of stiff source
FMDenaro is offline   Reply With Quote


stiff chemistry solver

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
swak4foam newbie29 OpenFOAM Installation 82 July 18, 2015 17:16
OpenFOAM Installation for navalFoam sachinlb OpenFOAM Installation 21 June 23, 2014 08:07
"parabolicVelocity" in OpenFoam 2.1.0 ? sawyer86 OpenFOAM Running, Solving & CFD 21 February 7, 2012 12:44
Source Terms in Momentum Balance vidyaraja Main CFD Forum 0 May 25, 2009 15:24
DecomposePar links against liblamso0 with OpenMPI jens_klostermann OpenFOAM Bugs 11 June 28, 2007 17:51

All times are GMT -4. The time now is 09:35.