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-   -   Problem with circle sampling type, of Sample utility (http://www.cfd-online.com/Forums/openfoam-post-processing/118446-problem-circle-sampling-type-sample-utility.html)

nik May 28, 2013 03:17

Problem with circle sampling type, of Sample utility
 
Hi,

I am trying to use the sample utility to extract data along a circular line. To do so, I am using the "circle" sampling type. The problem that I have is that in the first column of the output file, where theta should be, I always get zeros. This "circle" type is not listed in the users guide, so the following dictionary that I am using is a result of trial and error, and by looking at the source sampleSet.H. So I am not sure if I am using all the right parameters.

This is the sampleDict that I am using:

Code:

interpolationScheme cell;
setFormat          raw;

sets
(
    alongCircWall
    {
        type        circle;
        origin      (0 0 0);    // Origin (x, y, z) in global cartesian co-ordinates
        circleAxis  (1 0 0);    // Axis of the circle
        startPoint  (0 0 0.6);  // Defines start point on circle (x, y, z) in global cartesian co-ordinates
        dTheta      2;          // Sampling interval in degrees about the origin
        axis        x;          // This I don't know why is needed, but needs to be defined as well?
    }
);

fields              ( T );

By the way, I am using OpenFOAM 2.2.x. Any help would be appreciated.

Regards,
Nicolas

nik May 30, 2013 08:14

Figured it out
 
I have figured it out after all.

The problem was with the "axis x;" parameter. This parameter defines which coordinates are to be written in the output file for each point. You can select, x, y, z, for a single coordinate, or xyz for all coordinates. Since writing the angle theta is not an option, I used xyz to get the coordinates of each point along the circle, and some awk commands to calculate the angle.

It is also worth notting that this sampling type writes out the data along the circle in a weird order. So before plotting the values of a field versus the angle theta, you need to take a close look in the order in which the points are written.

Nicolas

daniel54431 February 23, 2015 12:01

Circle sampling on boundary patch
 
Hello all,

i know this thread is a bit older but my question fits in this thread very well.
I try to use the circle sample to get circular distributed values from
a boundary patch (e.g. wallheatflux) from a pipe.
The problem is when I set dTheta=1 for example I do not receive
360 values from 360 points, I just get around 50 values from 50 points.
For the remaining points I get the message:

Code:

--> FOAM Warning :
    From function void circleSet::calcSamples(DynamicList<point>&, DynamicList<label>&, DynamicList<label>&, DynamicList<label>&, DynamicList<scalar>&) const
    in file sampledSet/circle/circleSet.C at line 128
    Unable to find cell at point id 45 at location (0.0248137 0.00304673 0.5)

The points are definitely in the domain.
So how could it be, that OF finds no cells for interpolation
at most points?


Thanks for help.

Regards,

Daniel


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