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-   -   Display regions central linear and upwind for gamma scheme (http://www.cfd-online.com/Forums/openfoam-post-processing/61389-display-regions-central-linear-upwind-gamma-scheme.html)

braennstroem May 12, 2008 13:26

Hi, has anyone a hint, how
 
Hi,

has anyone a hint, how to display regions of central differencing and upwind scheme when using gamma (and filteredLinear)? I am having trouble to understand the implementation and would like to postprocess the use of the schemes...

Fabian

eugene May 13, 2008 05:33

Not a bad idea, but I don't th
 
Not a bad idea, but I don't think anyone has ever done this - at least I haven't seen any pictures to this effect.

Your first problem is that the discretization is defined for the faces of the mesh, not the cells, so you wouldn't be able to look at the raw results in a post-processor.
Secondly, the interpolation schemes do not have references to the database within their scope, so you can't access registered fields without major effort.

Should you have a solution for this, I would simply proceed to calculate the limiter for each face using the existing schemes outside of the solution loop and then check the value of the limiter to determine how much blending is being used. You would require some understanding of how the limiters are constructed and their method parameters are defined, so I wouldn't consider this a simple exercise.

braennstroem May 14, 2008 08:42

Thanks. I just tried to insert
 
Thanks. I just tried to insert a simple 'Info' statement into Gamma and filteredLinear files writing out phict and the limiter.
I understand the postprocessing problems, but would'nt it be possible to average the limiter for each cell and write those values inside of the interpolation schemes!?

Fabian

braennstroem May 28, 2008 03:49

One way to calculate the limit
 
One way to calculate the limiter is to collect the neighbouring values and calculate the limter by hand, but how is this done for an arbitrary cell. What are in these cases the upwind and downwind cells?

Fabian


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