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Replace NaN values with zero in COMSOL
Posted Feb 7, 2024, 8:38 a.m. EST Interfacing, API, Structural Mechanics Version 5.6 1 Reply
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Hello,
I use COMSOL to obtain eigenfrequencies of a 3D crystal with a point defect. I am a beginner with COMSOL.
For each eigenfrequency, I have a mode with a certain mode shape (amplitude). I only consider out-of-plane motion, i.e. w(x, y).
The COMSOL solution (the amplitude w) looks reasonable (from a physics point of view), but contains small numerical artefacts.
This is problematic as I want to calculate second-order derivates: d(d(w, x), x). In particular, evaluating this derivative yiels several NaN values.
My current solution is to export the data to Python, and process it there. I evaluate the derivative on a pretty large grid (5000x5000), so exporting all this data is cumbersome.
I have two ideas where I appreciate your input: Does COMSOL allow to replace NaN values with zeros without using a third-party program? I'm aware that the isnan() operator exists, but unsure if it suits the above purpose.
If not: What's the fastest way to export data from COMSOL (i.e. which program should I use)? I'm aware that links to Matlab and other languages exist, but wonder if they are faster.
Thanks
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Hi Leo,
You should be able to replace NaN values with zeros using an expression like:
if(isnan(d(d(w,x),x)),0,(d(d(w,x),x)))
An easier syntax for the second space derivative would be wxx.
A standard way to export data is to use the features under Results>Export to export the data to a text file, for example.
Best regards,
Magnus