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-   -   Interpolation on a 3D grid (http://www.cfd-online.com/Forums/openfoam-programming-development/102754-interpolation-3d-grid.html)

Tobi June 1, 2012 08:39

Interpolation on a 3D grid
 
Hi all,

i am not sure where to put that threat into and hope thats okay. :rolleyes:
Its not an especially question to openfoam but maybe some of you know the math descriptions about that. So my question is:

Do anyone know a equation, math construct or references for interpolation on a 3D grid.
Well I am just interested in the equations or the general description of such a problem.

An example:

You `ve a scalar value phi (like temperature, cp, mu, or sth. like that) depended on two variables like Z and Z".
You solve two transport equations with openFoam to get Z and Z" and wanna get phi out of a table. The table is a three-dimensional graphic like described befor. The problem is, that phi is generated with some grid points e.g. 100 points in Z direction an 40 points in Z" direction.

So if you get values for f and f" not being direct on a given point on the grid you have to interpolate the value phi.
Well I have a solution and know how it works but do not know if there are special literature or references.
The interpolation used in my case is shown here (my post too):

http://www.matheboard.de/thread.php?...ightuser=52671


well hope someone can give me an advice.

tobi

Arnoldinho June 1, 2012 08:53

Hi,

you could e.g. have a look at the 'Shepard Method', which is distance weighted interpolation in 3D: http://www.ems-i.com/gmshelp/Interpo...rds_Method.htm.
I'm not sure if this it directly want you need, but I successfully use it e.g. for surface terrain interpolation.

Greetings,

Arne

Tobi June 1, 2012 11:44

1 Attachment(s)
hi,

thx for your replay. Its sounds interessting but I am not sure if its the correct one like mine.

I am not very familiar with those interpolations.
Can you have a look at the PDF? Do anyone know sth. like that?

Thx in advance and I ll check your link and the equations again.
Tobi


here its like area weighted

Arnoldinho June 2, 2012 10:50

No, I unfortunately do not know this interpolation type.
But what exactly are you looking for now? The name and theory of your interpolation given in the pdf, or an alternative for this?

Greetings,
Arne

Tobi June 2, 2012 11:01

Quote:

Originally Posted by Arnoldinho (Post 364423)
No, I unfortunately do not know this interpolation type.
But what exactly are you looking for now? The name and theory of your interpolation given in the pdf, or an alternative for this?

Greetings,
Arne


Hi Arne, i am looking for the name and theory of that interpolation in my case ... but thx for your advice


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