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How to simplify the 3D axisymmetric model???

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in 2D and 1D model, we can select the axisymmetric to simplify the calculation. but in 3D model, how to simplify the calculation?
for example, the whole model is a cylinder, 1/4 of the model is sufficient for the calculation. but how to figure it out?
I even can not find any symmetry boundary condition in the acoutics moudle.

any reply is appreicated..

best wishes.

KYO

1 Reply Last Post Apr 2, 2011, 10:31 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Apr 2, 2011, 10:31 a.m. EDT
Hi

the symmetry ad antisymmetry BC's are there, normally as subnodes (try to right click on the different nodes, and follow the arrows such as "more".
Another thing, in the options/preferences select "show more options" I suggest also to select the "Show Equations", this adds a sub node with the underlaying equations, it helps to identify the variable names, and in the main physics nodes you have an "Advanvced Settings - Show all model inputs". By default, COMSOL does not show you everything, to not overload you with info you do not always need. I'm not sure if the symmetry and antisymmetry BC nodes are really hidden, but in this way you get all node anyhow ;)

I no neither not ahve the accoustincs module so for each physics things are slightly differents (the options available, not the methodology) but I'm sure you have boundary BC symmetry and antisymmetry.

The thing is that you must perform several runs when looking at modes with symmetries in 3D, by alternating the symmetry and anti-symmetry conditions, as these imposes limitations that only selects some subsets of all modes, be aware (this could be a reason to hide symemtry BCs and access it only for "advanced users")

--
Good luck
Ivar
Hi the symmetry ad antisymmetry BC's are there, normally as subnodes (try to right click on the different nodes, and follow the arrows such as "more". Another thing, in the options/preferences select "show more options" I suggest also to select the "Show Equations", this adds a sub node with the underlaying equations, it helps to identify the variable names, and in the main physics nodes you have an "Advanvced Settings - Show all model inputs". By default, COMSOL does not show you everything, to not overload you with info you do not always need. I'm not sure if the symmetry and antisymmetry BC nodes are really hidden, but in this way you get all node anyhow ;) I no neither not ahve the accoustincs module so for each physics things are slightly differents (the options available, not the methodology) but I'm sure you have boundary BC symmetry and antisymmetry. The thing is that you must perform several runs when looking at modes with symmetries in 3D, by alternating the symmetry and anti-symmetry conditions, as these imposes limitations that only selects some subsets of all modes, be aware (this could be a reason to hide symemtry BCs and access it only for "advanced users") -- Good luck Ivar

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