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Periodic Conditions

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Hello everyone,

I'm trying to solve a problem with periodic boundary conditions. If I set periodic conditions with the type of continuity on a geometry of a cube, and then a prescribed displacement on a face, then the cube moves in space, but does not experience deformation because the displacement of 2 opposite faces is equal.

Does anyone know how i can set periodic conditions such that the the cube will experience deformation?

In the model library of Comsol there is an example of Floquet periodicity, but I haven't seen one of continuity...

Thanks

3 Replies Last Post 15 févr. 2012, 07:30 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 15 févr. 2012, 02:14 UTC−5
Hi

for me it sounds like you have "antiperiodical" loads, but you want symmetry, no ?

--
Good luck
Ivar
Hi for me it sounds like you have "antiperiodical" loads, but you want symmetry, no ? -- Good luck Ivar

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Posted: 1 decade ago 15 févr. 2012, 04:40 UTC−5
Well, I want to set it up so that

U_right - U_left = (F - I ) *X

where F is the deformation gradient, U_left and U_right are the displacements of the left and right faces of the cube, I is the identity tensor and X is the distance between the faces.

However, i'm not sure of how to impose this condition...
Well, I want to set it up so that U_right - U_left = (F - I ) *X where F is the deformation gradient, U_left and U_right are the displacements of the left and right faces of the cube, I is the identity tensor and X is the distance between the faces. However, i'm not sure of how to impose this condition...

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

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Posted: 1 decade ago 15 févr. 2012, 07:30 UTC−5
Hi

I believe that is what the "solid" physics "Periodic condition BC" imposes (the underlaying equation is slightly cryptic with "if" and "src & dst" names).
Then up to you to decide how many DoF you constrain, and how they are aligned w.r.t the global coordinate transform

--
Good luck
Ivar
Hi I believe that is what the "solid" physics "Periodic condition BC" imposes (the underlaying equation is slightly cryptic with "if" and "src & dst" names). Then up to you to decide how many DoF you constrain, and how they are aligned w.r.t the global coordinate transform -- Good luck Ivar

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