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

Linear solvers in OpenFOAM

Register Blogs Community New Posts Updated Threads Search

Like Tree8Likes
  • 3 Post By akidess
  • 1 Post By cryabroad
  • 4 Post By akidess

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 26, 2019, 04:49
Default Linear solvers in OpenFOAM
  #1
New Member
 
Rahul
Join Date: Aug 2018
Posts: 6
Rep Power: 8
blue_arrow98 is on a distinguished road
Hey guys, I am doing a project on OpenFOAM simulating external flow over an airfoil. I am confused with various linear solvers available to solve the problem in the fvSoultion file.

Can anyone explain me the difference between GAMG and PCG solver for pressure and when is each one of them used?
blue_arrow98 is offline   Reply With Quote

Old   June 26, 2019, 12:34
Default
  #2
Senior Member
 
Santiago Lopez Castano
Join Date: Nov 2012
Posts: 354
Rep Power: 15
Santiago is on a distinguished road
Geometric Agglomerated MultiGrid

Parallel Conjugate Gradient

easy enough to look on the interwebs
Santiago is offline   Reply With Quote

Old   June 27, 2019, 03:45
Default
  #3
Senior Member
 
akidess's Avatar
 
Anton Kidess
Join Date: May 2009
Location: Germany
Posts: 1,377
Rep Power: 30
akidess will become famous soon enough
Quote:
Originally Posted by Santiago View Post
Geometric Agglomerated MultiGrid

Parallel Conjugate Gradient

easy enough to look on the interwebs
AFAIK -> PCG = Preconditioned Conjugate Gradient.
__________________
*On twitter @akidTwit
*Spend as much time formulating your questions as you expect people to spend on their answer.
akidess is offline   Reply With Quote

Old   June 27, 2019, 04:11
Default
  #4
Senior Member
 
Santiago Lopez Castano
Join Date: Nov 2012
Posts: 354
Rep Power: 15
Santiago is on a distinguished road
Quote:
Originally Posted by akidess View Post
AFAIK -> PCG = Preconditioned Conjugate Gradient.
I stand corrected
Santiago is offline   Reply With Quote

Old   June 30, 2019, 06:22
Default
  #5
Senior Member
 
Ruiyan Chen
Join Date: Jul 2016
Location: Hangzhou, China
Posts: 162
Rep Power: 10
cryabroad is on a distinguished road
Interesting topic! You can check out the following link to get some insights.

https://www.openfoam.com/documentati...e-solvers.html

Note there are GAMG preconditioners for PCG solvers, which is NOT the GAMG solver(belongs to the Multigrid solver catagory). By the way I remember some people stating that PCG solvers are better than GAMG for parallel computing. Is this true? What is the reason behind it?
blue_arrow98 likes this.
cryabroad is offline   Reply With Quote

Old   July 2, 2019, 04:04
Default
  #6
Senior Member
 
akidess's Avatar
 
Anton Kidess
Join Date: May 2009
Location: Germany
Posts: 1,377
Rep Power: 30
akidess will become famous soon enough
Quote:
Originally Posted by cryabroad View Post
By the way I remember some people stating that PCG solvers are better than GAMG for parallel computing. Is this true? What is the reason behind it?
More grids means more communication overhead. Not that important for small parallel simulations, but can become important for massive sims.
__________________
*On twitter @akidTwit
*Spend as much time formulating your questions as you expect people to spend on their answer.
akidess is offline   Reply With Quote

Old   July 2, 2019, 23:37
Default
  #7
Senior Member
 
Ruiyan Chen
Join Date: Jul 2016
Location: Hangzhou, China
Posts: 162
Rep Power: 10
cryabroad is on a distinguished road
Thanks for the explanation!

Ruiyan
cryabroad is offline   Reply With Quote

Reply

Tags
gamg, linear solver, pcg


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
ofgpu v1.1: GPU Linear Solvers for OpenFOAM Released gocarts OpenFOAM Announcements from Other Sources 4 March 8, 2019 12:21
OpenFOAM Training Jan-Apr 2017, Virtual, London, Houston, Berlin cfd.direct OpenFOAM Announcements from Other Sources 0 September 21, 2016 12:50
OpenFOAM Training, London, Chicago, Munich, Houston 2016-2017 cfd.direct OpenFOAM Announcements from Other Sources 0 September 14, 2016 04:19
Superlinear speedup in OpenFOAM 13 msrinath80 OpenFOAM Running, Solving & CFD 18 March 3, 2015 06:36
Water pump OpenFOAM 15 ANSYS CFX 110 comparation waynezw0618 OpenFOAM Running, Solving & CFD 39 March 5, 2009 13:57


All times are GMT -4. The time now is 07:38.