# How to calculate the field value of a arbitrary point

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 April 11, 2005, 04:13 Given a position as (x,y,z), I #1 Member   Luckyluke Join Date: Mar 2009 Posts: 51 Rep Power: 10 Given a position as (x,y,z), I want the u or p value in this point by using interpolation. Thanks all.

 April 11, 2005, 05:20 As a postprocessing step use t #2 Super Moderator   Mattijs Janssens Join Date: Mar 2009 Posts: 1,419 Rep Power: 18 As a postprocessing step use the 'sample' utility. Inside a code use the probe functionality (See e.g. oodles/createProbes.H). This does no interpolation however.

 April 11, 2005, 06:51 Hi,Mattijs. I can find out the #3 Member   Luckyluke Join Date: Mar 2009 Posts: 51 Rep Power: 10 Hi,Mattijs. I can find out the cell which contain the given point (x,y,z) using mesh.finCell(), then how I can know the cell's neighbour cells? Thanks.

 April 11, 2005, 07:18 vector probePoint(x,y,z); lab #4 Senior Member   Eugene de Villiers Join Date: Mar 2009 Posts: 725 Rep Power: 14 vector probePoint(x,y,z); label probeCell = mesh.findCell(probePoint); const labelList& probeCellNeighbours = mesh.cellCells()[probeCell]; forAll(probeCellNeighbours, cellI) { Do your stuff } But if you want to interpolate, you might want to look at the built-in interpolation classes.

 April 11, 2005, 08:13 Thank all. By the way, if I kn #5 Member   Luckyluke Join Date: Mar 2009 Posts: 51 Rep Power: 10 Thank all. By the way, if I knew the 'label' of one cell,e.g. cellI, then I can access the field value of this cell using U[cellI]. Is that right? Can a field loop be performed as follows: forALL(mesh.cells(),i) {U[i]=...} Or forALL(U,i) {U[i]=...}? These are simple questions. Could anybody give me a answer?

 April 11, 2005, 08:25 Right Both forALL(mesh.ce #6 Senior Member   Eugene de Villiers Join Date: Mar 2009 Posts: 725 Rep Power: 14 Right Both forALL(mesh.cells(),i) {U[i]=...} and forALL(U,i) {U[i]=...} will give you the same result, i.e. the ordering of cells and volFields are identical. Most operations however do not require that you loop over the cells explicitly as they can be performed using field algebra.

October 19, 2012, 05:45
How can get my results at the patch using points' coordinates
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Quote:
 Originally Posted by eugene vector probePoint(x,y,z); label probeCell = mesh.findCell(probePoint); const labelList& probeCellNeighbours = mesh.cellCells()[probeCell]; forAll(probeCellNeighbours, cellI) { Do your stuff } But if you want to interpolate, you might want to look at the built-in interpolation classes.

Hello,

I need the same BUT!:

I am doing a comparison between wind tunnel results and OpenFOAM simulation. Available from wind tunnel are the pressure coefficients (Cp) on 32 points. The coordinates of those points are available. I need to get P field on the body patch at those 32 points.

I mean, the coordinates of a point may not guarantee that It belongs to the patch (due to lack of accuracy of snappyHexMesh). How can get my results at the patch using points' coordinates?

February 28, 2014, 16:14
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Ripudaman Manchanda
Join Date: May 2013
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HFS, were you able to find a solution to your problem? I have a similar concern. I am using stressAnalysisFoam and I need the D field on the body patch at a particular point as well.

Quote:
 Originally Posted by hfs Hello, I need the same BUT!: I am doing a comparison between wind tunnel results and OpenFOAM simulation. Available from wind tunnel are the pressure coefficients (Cp) on 32 points. The coordinates of those points are available. I need to get P field on the body patch at those 32 points. I mean, the coordinates of a point may not guarantee that It belongs to the patch (due to lack of accuracy of snappyHexMesh). How can get my results at the patch using points' coordinates?

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