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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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mathematics and pde

Posted Dec 17, 2018, 10:20 p.m. EST General, Parameters, Variables, & Functions, Equation-Based Modeling Version 4.2a 3 Replies

Nikhil Valsan Kulangareth
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my variables are Ve1, Vi1, U1.

In pde equation when I substitute these variables in the source term, they appear in light brown color.

Why is this so? Attaching screenshots.

Somebody please help/ Thanks in advance.

Attachments:

3 Replies Last Post Dec 19, 2018, 8:46 a.m. EST
Jeff Hiller COMSOL Employee

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Posted: 6 years ago Dec 18, 2018, 4:06 p.m. EST

That's COMSOL's way of warning you that the dimensions of your inputs are inconsistent with what the software was expecting. From your screenshot, the source terms are expecting inputs with a dimension of 1/length^2 (i.e. units of 1/m^2).

Best,

Jeff

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Jeff Hiller
That's COMSOL's way of warning you that the dimensions of your inputs are inconsistent with what the software was expecting. From your screenshot, the source terms are expecting inputs with a dimension of 1/length^2 (i.e. units of 1/m^2). Best, Jeff
Nikhil Valsan Kulangareth
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Posted: 6 years ago Dec 18, 2018, 8:12 p.m. EST

I found that the simulation completed though the entry is inconsistent. In such case what value is assumed for these ? is the software completing the simulation asssuming the values to be zero ?

I found that the simulation completed though the entry is inconsistent. In such case what value is assumed for these ? is the software completing the simulation asssuming the values to be zero ?
Jeff Hiller COMSOL Employee

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Posted: 6 years ago Dec 19, 2018, 8:46 a.m. EST

Yes, it's a warning, not an error, so the software can complete the run, but it is pointing out a location where you may have made a mistake. If you know what you are doing, you can ignore that warning. A typical case where you would ignore the warning is if you intentionally left out a multiplicative constant that would have given the right dimension to your input. For example, if an input field expects a force (N), and you type a displacement (m) because you know that the associated stiffness is 1[N/m].

Jeff

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Jeff Hiller
Yes, it's a warning, not an error, so the software can complete the run, but it is pointing out a location where you may have made a mistake. If you know what you are doing, you can ignore that warning. A typical case where you would ignore the warning is if you intentionally left out a multiplicative constant that would have given the right dimension to your input. For example, if an input field expects a force (N), and you type a displacement (m) because you know that the associated stiffness is 1[N/m]. Jeff

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