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Strange mesh for the model

hi everybody,
i'm new in this forum, and i'm new to use comsol.

for a thesis work i've to model the Laser Ultrasonics Physics.
i've already read some posts and download some pdf about it, but there are some problems to resolve.

the electromagnetic wave penetrate in the model for about 10nm, and the spot laser is 6mm of diameter.

i didn't use the EM physic, but i can built the same effect just using the thermal stress.

the question is:

since it's impossibile to mesh all in one model, i'd like to separe the model in two different sub models:
the first should be only the thermal expansion (little volume)
the second should be the acoustic transient in the material (ultrasonics wave) (big volume)

i would take the displacement field of the first one solution and put in the second one.
the problem is:
have i to export displacement by hand!?
is there a method to do the two model and two physics in the same working area, e.g. deselecting some parts of the model?

if i'm in the wrong way, and you have got some different ideas, please help me.

fabrizio

1 Reply Last Post Oct 9, 2012, 6:53 AM EDT
Posted: 5 years ago Oct 9, 2012, 6:53 AM EDT
Hi, Fabrizio

Many wises will be able to help you with your exact problem. But about the question if in COMSOL you can do both "models", the answer ---as far as I know--- is yes. And I write "models", because in COMSOL both domains can be solved as an only one model (by building only one geometry and selecting different physics at different domains, and coupling them at the common boundary) or even by creating two models in the same file, and connecting them through global variables. I think in this case you can use the first option.

In case you choose the first (and simpler) option, i.e. one geometry and different physics, don't worry about the different scales, COMSOL can do a very good job with the mesh, although perhaps you have to help him (for instance, a much finer mesh at tiny pieces, or boundary layer mesh at the interface boundary).

Bye,

Jesus.
Hi, Fabrizio Many wises will be able to help you with your exact problem. But about the question if in COMSOL you can do both "models", the answer ---as far as I know--- is yes. And I write "models", because in COMSOL both domains can be solved as an only one model (by building only one geometry and selecting different physics at different domains, and coupling them at the common boundary) or even by creating two models in the same file, and connecting them through global variables. I think in this case you can use the first option. In case you choose the first (and simpler) option, i.e. one geometry and different physics, don't worry about the different scales, COMSOL can do a very good job with the mesh, although perhaps you have to help him (for instance, a much finer mesh at tiny pieces, or boundary layer mesh at the interface boundary). Bye, Jesus.

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