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

increasing Courant number

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 4, 2016, 06:48
Default increasing Courant number
  #1
Senior Member
 
CFD_Lovers
Join Date: Mar 2015
Posts: 168
Rep Power: 11
sinatahmooresi is on a distinguished road
Hi friends!
I'm modeling a submerged buoyant turbulent jet of brine in ambient water tank. it is obvious to use a multiphase solver for this modeling. I'm dealing with twoPhaseEulerFoam solver of OoenFOAM. i prepared the model for run. but with setting the time step about 0.005 i faced the increasing of Courant number in each time step. for example after three time steps it reaches to 9 and then to 600 for time 4*0.005!!!
i know it could be emanated from many aspect of setting of model. but is there any body to help me with this ?
all the bests
sinatahmooresi is offline   Reply With Quote

Old   April 4, 2016, 11:01
Default
  #2
Senior Member
 
Mahdi Hosseinali
Join Date: Apr 2009
Location: NB, Canada
Posts: 273
Rep Power: 18
anishtain4 is on a distinguished road
Check your residuals, usually when CFL overshoots one of the residuals is getting out of bound which causes the CFL number to get high (at this point your velocities are very hight, CFL= VL/nu where L is grid size). This divergence can have many various reasons which is hard to say not knowing anything from your output or problem set up, but a common cause of it is boundary conditions.
anishtain4 is offline   Reply With Quote

Old   April 5, 2016, 23:58
Default Courant Number
  #3
Member
 
Akr
Join Date: Apr 2015
Location: India
Posts: 53
Rep Power: 11
NightWing is on a distinguished road
Courant Number Shoot up can be due to wide variety of reasons. Initially it's better to choose a deltat value in accordance with your input velocity magnitude if at all u r using a velocity input as a boundary condition. Make sure it falls within the range of deltat< mag(U)/smallets element size. it can also be due to poor mesh quality at certain times. As its a multiphase flow, i would request you to check the pressure boundary conditions with atmost care.
NightWing is offline   Reply With Quote

Reply


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
TwoPhaseEulerFoam high courant number mwaqas OpenFOAM Running, Solving & CFD 11 July 11, 2017 14:19
Difference between courant number and acoustic courant number? umair64 CFX 1 September 1, 2015 18:41
Sudden jump in Courant number NJG OpenFOAM Running, Solving & CFD 7 May 15, 2014 13:52
[blockMesh] --> foam fatal error: lillo763 OpenFOAM Meshing & Mesh Conversion 0 March 5, 2014 10:27
IcoFoam parallel woes msrinath80 OpenFOAM Running, Solving & CFD 9 July 22, 2007 02:58


All times are GMT -4. The time now is 11:26.