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Geometry allows specification of units, but physics are in SI

Posted Mar 11, 2011, 6:18 p.m. EST Version 4.0, Version 4.0a, Version 4.1 2 Replies

Tyler
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Riddle me this:

What is the point of allowing the geometry units to be modified, but having the physics take SI units?

For example, setting length unit to inches in the geometry, add Solid Mechanics (physics) and the thickness is in meters, the Linear Elastic Material Model wants Young's modulus in Pa.

Am I missing something? Really what is the point in even offering to change units in geometry. You're going to do a conversion somewhere along the line....
2 Replies Last Post Mar 14, 2011, 2:34 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 12, 2011, 4:34 a.m. EST
Hi

what do you have against the units ? Have you done your homework and read the doc ? You can select the units of your preferrence (see attachedfile, but you should do it before you enter a model as else all conversion of number without units in default unit cells will not follow (how could COMSOL know ?)

I find the units feature the most usefull approach in COMSOL, it has saved me hundred of hours work, because unit coherence check is a mandatory task when you do engineering for critical constructions many fatal accixents have happne because of bad unit conversion)

So basically I do not understand your riddle there ;)

--
Good luck
Ivar
Hi what do you have against the units ? Have you done your homework and read the doc ? You can select the units of your preferrence (see attachedfile, but you should do it before you enter a model as else all conversion of number without units in default unit cells will not follow (how could COMSOL know ?) I find the units feature the most usefull approach in COMSOL, it has saved me hundred of hours work, because unit coherence check is a mandatory task when you do engineering for critical constructions many fatal accixents have happne because of bad unit conversion) So basically I do not understand your riddle there ;) -- Good luck Ivar

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Tyler
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Posted: 1 decade ago Mar 14, 2011, 2:34 p.m. EDT

You can select the units of your preferrence (see attachedfile, but you should do it before you enter a model as else all conversion of number without units in default unit cells will not follow


Ivar, thanks for your reply. I have found the settings box from your attached image. This is the item "Unit System" under "Model" which seems to allow override of the defaults on a per model basis.

There is also a "Unit System" under the root item (mph filename) which apparently sets the default units for the whole file.

Thank you for pointing this out, I completely missed the settings. Searching in the Documentation, there is certainly mention of the ability to change units, but it never actually indicates where (in the program) the settings are made.
[QUOTE] You can select the units of your preferrence (see attachedfile, but you should do it before you enter a model as else all conversion of number without units in default unit cells will not follow [/QUOTE] Ivar, thanks for your reply. I have found the settings box from your attached image. This is the item "Unit System" under "Model" which seems to allow override of the defaults on a per model basis. There is also a "Unit System" under the root item (mph filename) which apparently sets the default units for the whole file. Thank you for pointing this out, I completely missed the settings. Searching in the Documentation, there is certainly mention of the ability to change units, but it never actually indicates where (in the program) the settings are made.

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