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Evaluation of a value at a specific point within a Cut Point 3D Grid Dataset

Posted 19 févr. 2025, 09:52 UTC−5 Electromagnetics, Results & Visualization Version 6.3 5 Replies

Mark Harradine
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Hopefully a quick and easy one!

I have created a 3D simulation of an arc magnet that moves around in space, and want to evaluate the z component of field at specific points within a 3D Cut Point dataset.

Obviously if the dataset had 1 discrete point, I would just evaluate mfnc.Bz for the dataset.

However, with a grid definition of the dataset (see attachment) I want to evaluate it at a specific point within that grid definition. I have customised the point number variable to be "chip_n" so clearly need to use that within my expression to evaluate, but I cannot determine what the correct syntax for this is!

In my attached example there are 54 discreet points defined by my grid, and I would like (for example) to determine the difference in the z field at points 1 and 10.

Thanks in advance for your guidance...

Mark

Attachments:

5 Replies Last Post 25 févr. 2025, 05:17 UTC−5
Edgar J. Kaiser Certified Consultant
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Posted: 8 months ago 19 févr. 2025, 13:26 UTC−5

Hi Mark,

just a wild guess: could withsol() do the trick.

Cheers Edgar

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi Mark, just a wild guess: could withsol() do the trick. Cheers Edgar
Mark Harradine
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Posted: 8 months ago 20 févr. 2025, 06:17 UTC−5

Hi Edgar,

I did try looking into using "withsol()", but I still couldn't see how to develop an expression that drills down to an individual point within a dataset. The examples in the manual don't really relate to what I am trying to achieve.

Thanks for the idea though!

Will let you know if I find out a suitable method.

Mark

Hi Edgar, I did try looking into using "withsol()", but I still couldn't see how to develop an expression that drills down to an individual point within a dataset. The examples in the manual don't really relate to what I am trying to achieve. Thanks for the idea though! Will let you know if I find out a suitable method. Mark
Gunnar Andersson COMSOL Employee

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Posted: 8 months ago 21 févr. 2025, 10:30 UTC−5

There's no expression syntax for referring to a point that has a certain value of chip_n. It might be possible to do what you want using a Point Evaluation in a Derived Values or an Evaluation Group: I think that the points are ordered in increasing order with respect to chip_n, and if they aren't, then you can evaluate chip_n in addition to the expression that you are interested in. This leaves you with a table of values. You can create a model method that extracts the values you're interested in. This is admittedly more complicated that a dedicated expression syntax would have been.

There's no expression syntax for referring to a point that has a certain value of chip_n. It might be possible to do what you want using a Point Evaluation in a Derived Values or an Evaluation Group: I think that the points are ordered in increasing order with respect to chip_n, and if they aren't, then you can evaluate chip_n in addition to the expression that you are interested in. This leaves you with a table of values. You can create a model method that extracts the values you're interested in. This is admittedly more complicated that a dedicated expression syntax would have been.
Edgar J. Kaiser Certified Consultant
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Posted: 8 months ago 21 févr. 2025, 12:35 UTC−5

Can a filter expression help in a point plot?

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Can a filter expression help in a point plot?
Mark Harradine
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Posted: 8 months ago 25 févr. 2025, 05:17 UTC−5

I think the best available solution is to use the at function.

For example, to evaluate mfnc.Bz at a position of (x1,y1,z1), you would use:

at3_spatial(x1,y1,z1,mfnc.Bz)

This is for a 3D model, you would use at1 or at2 for lower dimensions.

As alluded to above, I do not think the object model drills down to the granular level needed to expose the individual locations of a Cut Point grid dataset.

I think the best available solution is to use the ***at*** function. For example, to evaluate mfnc.Bz at a position of ***(x1,y1,z1)***, you would use: ***at3_spatial(x1,y1,z1,mfnc.Bz)*** This is for a 3D model, you would use at1 or at2 for lower dimensions. As alluded to above, I do not think the object model drills down to the granular level needed to expose the individual locations of a Cut Point grid dataset.

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