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How do you implement FEM model V&V with COMSOL ?

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Dear All
I followed an interesting webinar yesterday

www.nafems.org/events/nafems/2015/vvpredictive/

and I bough the book of Oberkampf. The issues discussed are essential for all modelling, but I find little on how best to apply V&V to multi-physics FEM, as we do commonly with COMSOL Multiphysics.

How do you do it ?

My way:
- analyse my model to get out the physics needed, the type of solver use (steady-state, time dependent frequency domain, pre-stressed ...) the interfaces and flow of physical quantities between the physics
- update: check the physics hypothesis versus the model dimensions are they valid ? this is less critical for COMSOL (except for ACDC/RF/Optics) than for older FEM as COMSOL is far more general, but should be done carefully, a 100m^3 oil rig looks the same as a mm^3 MEMS device on our screens but the domain to boundary ratio changes drastically and the physics hypothesis might not be valid for one or the other of our scale dimensions.
- build the models: one physics at the time !! (often by modifying some Application Library models)
- check the different sub models for simple cases against analytical solutions, and better, when available simple measured cases.

The latter is the best _verification_ approach I can do, for the rest I must rely on COSMOL's developers, and from all the other users i.e. the Forum

- I do often also check the mesh sensitivity of the results already on these simpler models

- build and run my complete model,
- check the mesh sensitivity (when possible as often these become very heavy),
- check results against a few analytical calculations and the sub models
- identify measurement check points to ask for when the model is build and is undergoing tests

- wait for test results from the device to _calibrate_ the model and to hopefully _validate_ it by complementary measurements.

Basically for one full multi-physics model, I can have made a few dozen simpler sub-models, this is now very easy and fast with COSMOL, and is the most efficient way I have found to progress with confidence in this multi-dimensional world of complex systems modelling

Comments appreciated :)

--
Have fun COMSOLing
Ivar

0 Replies Last Post May 29, 2015, 2:46 a.m. EDT
COMSOL Moderator

Hello Ivar KJELBERG

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