# Interpolation on a 3D grid

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 June 1, 2012, 08:39 Interpolation on a 3D grid #1 Super Moderator     Tobias Holzmann Join Date: Oct 2010 Location: Leoben (Austria) Posts: 1,835 Blog Entries: 6 Rep Power: 32 Sponsored Links Hi all, i am not sure where to put that threat into and hope thats okay. 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

 June 1, 2012, 08:53 #2 Senior Member   Arne Stahlmann Join Date: Nov 2009 Location: Hanover, Germany Posts: 209 Rep Power: 10 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

June 1, 2012, 11:44
#3
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Tobias Holzmann
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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?

Tobi

here its like area weighted
Attached Files
 schemes.pdf (52.0 KB, 18 views)

 June 2, 2012, 10:50 #4 Senior Member   Arne Stahlmann Join Date: Nov 2009 Location: Hanover, Germany Posts: 209 Rep Power: 10 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

June 2, 2012, 11:01
#5
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Tobias Holzmann
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Quote:
 Originally Posted by Arnoldinho 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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