CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Advice on projection/fractional step methods

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 4, 2017, 11:21
Default Advice on projection/fractional step methods
  #1
New Member
 
David
Join Date: Aug 2016
Posts: 6
Rep Power: 10
dajuno is on a distinguished road
Dear all,

I have a fully coupled unsteady FEM Navier-Stokes code, used in the context of hemodynamics, in particular flow through stenosis with Reynolds numbers of the order of ~2500. (I suspect the flow to be near transition; LES will be carried out later to confirm.)

I'd like to implement projection/fractional step/splitting methods for efficiency. There are many schemes and many names in the game, so I'd like to ask about your experiences and recommendations. What are your favorites?
In particular: implicit or explicit convection? Pressure treatment?

Thanks for your advice!

Regards
David
dajuno is offline   Reply With Quote

Old   July 4, 2017, 12:22
Default
  #2
Senior Member
 
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,887
Rep Power: 73
FMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura about
I always used the pressure-free projection method... Second order in time using explicit for the convection and the SGS terms and implicit for the diffusion.
FMDenaro is offline   Reply With Quote

Old   July 4, 2017, 18:09
Default
  #3
New Member
 
David
Join Date: Aug 2016
Posts: 6
Rep Power: 10
dajuno is on a distinguished road
Thanks for your comment. Can you elaborate on why you chose pressure-free (e.g. instead of incremental pressure correction)?
Are there any considerations w.r.t. BDF2 vs. Crank-Nicolson?

Thanks
dajuno is offline   Reply With Quote

Old   July 4, 2017, 18:32
Default
  #4
Senior Member
 
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,887
Rep Power: 73
FMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura about
Quote:
Originally Posted by dajuno View Post
Thanks for your comment. Can you elaborate on why you chose pressure-free (e.g. instead of incremental pressure correction)?
Are there any considerations w.r.t. BDF2 vs. Crank-Nicolson?

Thanks

In general, when well-formulated, these fractional methods are all quite good. A detailed analysis of each method does not lead to a definition of the "best one". I can say that each method produces a different meaning of the "pressure" field.

Then, BDF2 vs. Crank-Nicolson is something related only to the solution of the intermediate momentum equation. The CN scheme produces a stable solution and allows to work with reasonable time-step. The intermediate velocity must be prescribed at the boundary and this is, however, an issue to consider carefully. The BDF2 I used (Adams-Bashforth) is stable provided that the time-step is constrained by the (cfl-Re_h) stability region.

You can find a lot of published literature about that.
FMDenaro is offline   Reply With Quote

Reply

Tags
fem, fractional step, projection method

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
How to use PIMPLE properly? floquation OpenFOAM Running, Solving & CFD 27 August 12, 2024 11:15
courant number increases to rather large values 6863523 OpenFOAM Running, Solving & CFD 22 July 6, 2023 00:48
pimpleDyMFoam computation randomly stops babapeti OpenFOAM Running, Solving & CFD 5 January 24, 2018 06:28
Micro Scale Pore, icoFoam gooya_kabir OpenFOAM Running, Solving & CFD 2 November 2, 2013 14:58
same geometry,structured and unstructured mesh,different behaviour. sharonyue OpenFOAM Running, Solving & CFD 13 January 2, 2013 23:40


All times are GMT -4. The time now is 07:03.