How to find discretization schemes used in OF

md_lieber · February 8, 2011, 20:44

I've gotten a lot of help from this great group in the past, so hopefully someone can point me in the right direction for this:

I'm learning in class about equation discretizations for the fundamental PDEs required to CFD. We're looking at how different schemes can affect the soln stability and introduce phase errors, amplitude errors, etc. I'm trying to understand where these schemes are specified and, if not user-definable; what the default scheme is.

The fvSolution file seems to define the solver settings for each variation, is this unique, or do commercial CFD packages actually solve each variable using a different algorithm? If fvSchemes involves PDE discretization, I've never heard of selecting a scheme based on each operation or variable. I've only studied "Scheme X applied to the momentum equation". Can anyone explain the difference, or is fvSchemes performing some alternate function?

THANKS!!

akidess · February 15, 2011, 11:07

I'm pretty sure you can specify convergence criteria in every CFD package per variable. As for the solution algorithm, there might be less options but it should be possible to at least edit settings like the Multigrid cycle.

For fvSchemes, again there might be a bit more options as in other packages. But specifying which discretization to use for time stepping, gradient calculation and the discretization of the convective term should be fairly standard.

February 8, 2011, 20:44	How to find discretization schemes used in OF	#1
md_lieber New Member Join Date: May 2010 Posts: 6 Rep Power: 15	I've gotten a lot of help from this great group in the past, so hopefully someone can point me in the right direction for this: I'm learning in class about equation discretizations for the fundamental PDEs required to CFD. We're looking at how different schemes can affect the soln stability and introduce phase errors, amplitude errors, etc. I'm trying to understand where these schemes are specified and, if not user-definable; what the default scheme is. The fvSolution file seems to define the solver settings for each variation, is this unique, or do commercial CFD packages actually solve each variable using a different algorithm? If fvSchemes involves PDE discretization, I've never heard of selecting a scheme based on each operation or variable. I've only studied "Scheme X applied to the momentum equation". Can anyone explain the difference, or is fvSchemes performing some alternate function? THANKS!!

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February 15, 2011, 11:07		#2
akidess Senior Member Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,377 Rep Power: 29	I'm pretty sure you can specify convergence criteria in every CFD package per variable. As for the solution algorithm, there might be less options but it should be possible to at least edit settings like the Multigrid cycle. For fvSchemes, again there might be a bit more options as in other packages. But specifying which discretization to use for time stepping, gradient calculation and the discretization of the convective term should be fairly standard.