CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

CFL number limit for InterFoam

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

LinkBack Thread Tools Display Modes
Old   November 8, 2009, 10:33
Default CFL number limit for InterFoam
Senior Member
Suresh kumar Kannan
Join Date: Mar 2009
Location: Luxembourg, Luxembourg, Luxembourg
Posts: 129
Rep Power: 10
kumar is on a distinguished road
Hello everybody,
I have been using lesinterFoam for studying the breakup of liquid sheets. I have also been testing the solver for the CFL limit. Recently I read an article "Volume of fluid methods fro immiscible-fluid and free-surface flows" by Vinay R.Gopala, Berend G.M. van Wachem.Chemical Engineering Journal 141 (2008) 204-221

In this paper it has been specified a couple of times that for the inter gamma scheme that is implemented in interFoam it is required to have very small time steps, CFL<0.01 for keeping a sharp interFace. Based on tis comments I have done a comparative study of different CFL numbers for the same mesh and same boundary conditions.

I studied CFL numbmers of 0.2,0.1,0.05,0.01 and 0.0075 for the liquid sheets.

I found out that the cases are very much dependent on the CFL numbers, but the cases with CFL nummbers 0.01 and 0.0075 are closer to each other. Then I alos found in article by Henry Weller " Interface tracking capabilities of the Inter-Gamma Differencing scheme" that it ir required to use Co<1/2 for 2d cases and Co<1/3 for 3d cases.

Then it is also specified in Gopalas paper that in order to use larger time steps subcycles are used to solve the VOF equation. For a given Courant number, the flow equations are solved initially and later the VOF equation is fractionally updated n times, where n represents the number of subcycles predefined in the code.

Now my question is why has the CFL limit been specified differently in these two literatures, which one should I follow, should I follow the limit specified by Gopala in his paper to keep a sharp interface or the one specified by Henry in his article which looks quiet old to me.

My second question what is the limit to which i can vary my CFL number if I can use more n gamma subcycles.

Has anybody studied the accuracy of the solution by using higher CFL number basically higher time steps and increasing the ngamma subcycles.
I mean if want to use a CFL number of 0.2 is it sufficent that I use 4 ngamma subcycles or shouldi use more.
Is there any reference for this CFL limit and the ngamma subcycles.

with regards
K.Suresh kumar
kumar is offline   Reply With Quote


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
Mesh Refinement Luiz Eduardo Bittencourt Sampaio (Sampaio) OpenFOAM Mesh Utilities 42 January 8, 2017 13:55
DecomposePar unequal number of shared faces maka OpenFOAM Pre-Processing 6 August 12, 2010 09:01
BlockMeshmergePatchPairs hjasak OpenFOAM Native Meshers: blockMesh 11 August 15, 2008 07:36
Unaligned accesses on IA64 andre OpenFOAM 5 June 23, 2008 10:37
Trimmed cell and embedded refinement mesh conversion issues michele OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 2 July 15, 2005 04:15

All times are GMT -4. The time now is 12:14.