CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Programming & Development (http://www.cfd-online.com/Forums/openfoam-programming-development/)
-   -   fvc::reconstruct( ) algorithm (http://www.cfd-online.com/Forums/openfoam-programming-development/77943-fvc-reconstruct-algorithm.html)

tetraeder July 8, 2010 04:36

fvc::reconstruct( ) algorithm
 
Hi Foamers,

I am trying to figure out how the fvc::reconstruct( ) algorithm works. My first thought was:
Sum up the facefluxes multiplied with the facenormal over a cell and divide it by the sum of the magnitude of the facevector components of every face of the cell.
The algorithm in the "fvcReconstruct.C" file seems far more complex then my thought:

inv(surfaceSum(sqr(mesh.Sf())/mesh.magSf()))
& surfaceSum((mesh.Sf()/mesh.magSf())*ssf)


The second line is what I expected, but the first line is a little mystery to me.
Can anybody explain this to my, please?


Rainer

marupio July 8, 2010 09:31

Just a guess... it looks like it might be non-orthogonal correction...?

kjmaki July 9, 2010 11:15

Rainer, I agree with your description. The first line finds one over the square of the components of the area. The second line has the the components of the area in the numerator, so the result is just one over the area times the sum of what ever you are reconstructing. This is what you want for a face-area-weighted average.

There is another post by Henry which is relevant here:

http://www.cfd-online.com/Forums/ope...integrate.html

Kevin

sek March 16, 2011 13:27

I am also puzzled by what fvc:reconstruct does. Has anyone here figured what it does? It seems it is not based on any mathematical identity (like Gauss theorem), but some sort of approximation.

thibault_pringuey January 16, 2012 13:06

fvc::reconstruct explaination
 
1 Attachment(s)
Hello,

I have had a look at the fvc::reconstruct method. Please find attached an attempt to explain it.

Cheers,


Thibault

makaveli_lcf January 17, 2012 05:00

Thibault, excellent! Thank you for you work! Currently I am working on improving my model introducing a reconstruction for them... So hope to find some advantage on using it, will post some general conclusions.

cheng1988sjtu August 27, 2014 13:56

Hi makaveli_lcf,

Did you find any advantage using fvc::reconstruct ?

In my experience, using fvc::reconstruct seems too dissipative? need to find out what cause the dissipation, maybe due to the face-weighted averaging ?

Just curious, did you find anything similar?

Quote:

Originally Posted by makaveli_lcf (Post 339669)
Thibault, excellent! Thank you for you work! Currently I am working on improving my model introducing a reconstruction for them... So hope to find some advantage on using it, will post some general conclusions.



All times are GMT -4. The time now is 07:38.