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

Fractional Step Method interpretation

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

LinkBack Thread Tools Search this Thread Display Modes
Old   February 23, 2006, 09:12
Default Fractional Step Method interpretation
Jean-François Corbett
Posts: n/a
Dear all,

I am using the Fractional Step Method (FSM) for the first time, so I am really just trying to understand how it normally behaves. Despite some effort, I still cannot get it to work as it presumably should.

In accordance with (Perot 1993, 1995) and (Zang, Street & Koseff, 1994), I discretize the equations before performing the FSM factorization. In practice, this means that the boundary conditions chosen for the velocity u are applied to u*; is this right? So if, as in my case, you have no-slip at the bottom and a Dirichlet (e.g. u=u0) at the top, then u* will tend toward zero at the bottom and toward u0 at the top. (Perhaps this is where my interpretation is wrong?)

Then comes the pressure correction. If you already have u* tending toward 0 on the surface, then that would mean grad(p) should also tend toward 0 on the surface to yield u=0, i.e. constant pressure on the surface. As you point out, this does not make sense. How is one then supposed to apply the fractional step method?

By the way, I use a non-staggered, non-orthogonal grid.

Thanks in advance for your help!


  Reply With Quote

Old   February 27, 2006, 17:32
Default Re: Fractional Step Method interpretation
Posts: n/a
>In practice, this means that the boundary conditions chosen for the velocity u are applied to u*

Correct. Both of the B.C.'s you describe are Dirichlet.

>By the way, I use a non-staggered, non-orthogonal grid.

The non-staggered grid is probably the issue. Many of the fraction step/pressure correction methods have issues (like limitation to normal velocity B.C.'s, for example) if you try to use a non-staggered discretization. There are some versions that stagger only some of the flow variables, but I'm not sure if these methods are still in use.

  Reply With Quote

Old   March 1, 2006, 10:38
Default Re: Fractional Step Method interpretation
Frederic Felten
Posts: n/a

I have an article that I wrote (currently in press for the Journal of Computational Physics) where I spend some time really explaining the steps one has to follow with the fractional step method using a non-staggered, curvilinear, Finite volume approach. In addition, I discuss conservation issues (that might also be of interest to you).

Therefore, shoot me an email at so that I could email you my paper.


  Reply With Quote


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
MATLAB fractional step code Darren Main CFD Forum 7 September 25, 2018 14:58
Comparing between the Fractional step method and the SIMPLE method ghlee Main CFD Forum 1 April 10, 2012 16:59
Any fractional step solver around aldot OpenFOAM Running, Solving & CFD 0 February 22, 2008 06:19
BC for Pressure Equation in Fractional Step Method Márcio Main CFD Forum 0 January 24, 2007 05:22
Fractional step in ALE form - possible? Wee Main CFD Forum 2 October 3, 2006 10:20

All times are GMT -4. The time now is 23:19.