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-   -   Line probe problem (https://www.cfd-online.com/Forums/star-ccm/110088-line-probe-problem.html)

badger1 December 3, 2012 17:17

Line probe problem
 
I have put a line probe into a simulation but it does not seem to fill in all the points. it has random spaces where there are not points and the data is then missing when I use that line probe to plot a graph.

Does anyone how how to solve that?

Any help would be greatly appriciated.

harry123 June 12, 2017 11:31

Anyone can answer the above question please ?

MBdonCFD June 12, 2017 15:00

Are you looking at a geometry displayer of your probe points in a scene or their position in an XY plot? If you are looking at the XY plot, any probe point that lies in a cell will show the value of at that cell center. This is true whether you are talking about position, pressure, velocity or whatever. To get a smooth plot that shows the values at your actual probe positions you must enable 'smooth values' in the property window. XY Plot > Y Types > Y Type 1 (or 2, 3, etc...). This turns on node interpolated values.

MBdonCFD June 12, 2017 15:02

Sorry, I should have read closer. Can you show an image of this?

harry123 June 14, 2017 06:04

1 Attachment(s)
I meant like this, the line probe with points you can see in pic have been defined over the full length, but points turn up only in some areas.
If I plot some quantity on this line, the data is missing where there are no points shown

MBdonCFD June 14, 2017 09:00

Ah... Is this line probe on a boundary surface (inlet/outlet/etc...)? If that is the case, then some of your points are defined outside of the domain and therefore have no position or scalar data to plot or display. This could be the result of your volume mesh or how you defined the line probe. There are two things you can try that should fix this.

1) Edit the derived part and select the 'snap to part' option then select that face.

OR

2) Move the line probe some tiny distance upstream so that all the points fall within the domain.

harry123 June 14, 2017 09:39

Ah yes..!! I got the problem now.

Actually I was using snap to part (to my outlet), but the problem was that the x coordinate for point 2 of the line remains slightly outside boundary , (10^-15m difference !!!). But that was causing the problem.

I got it right now.

Really appreciate your genius, its awesome..!!

Thanks a lot

MBdonCFD June 14, 2017 09:42

Not a problem. Glad I could help.

me3840 June 15, 2017 14:46

Just for future reference, except for seeding streamline rakes I avoid using line probes at all costs. Wherever you need a line probe you can easily use a section plane (or a section plane of a section plane) to do the same thing more reliably.

harry123 June 19, 2017 07:31

Thanks for the advice, will keep that in mind.


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