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Boundary conditions in COMSOL 4.2a

Posted Jul 5, 2012, 7:00 p.m. EDT MEMS & Nanotechnology, MEMS & Piezoelectric Devices Version 4.2a 2 Replies

Jose Ivan Nieva
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Hi, i have one simple question.
In the MES module (EMI) the boundary conditions chargue zero. Is the total chargue zero? Or no exist chargues?
I'm using a dielectric material in my model and need polarized of the dipole of the material.
2 Replies Last Post Jul 9, 2012, 2:49 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 Jul 6, 2012, 3:23 a.m. EDT
Hi

check the underlaying equations, most BC applies to the field element value that is its locally "0", except for lumoed BC cases where the integrated value is "0"

--
Good luck
Ivar
Hi check the underlaying equations, most BC applies to the field element value that is its locally "0", except for lumoed BC cases where the integrated value is "0" -- Good luck Ivar
Jose Ivan Nieva
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Posted: 1 decade ago Jul 9, 2012, 2:49 p.m. EDT
Thanks Ivar.
With reference to attach file, consider a dielectric mass with two electrodes fixed to its surface. This construction is held at some small distance from a second dielectric mass which we wish to control. Imagine two molecules in the target dielectric placed symmetrically about the mid plane of the diagram. Creating a potential difference across the electrodes gives rise to a fringing field which polarises these molecules. Since the electric field is non-uniform the forces acting on the the positive and negative charges are not quite collinear leading to a resultant force on each molecule F1, F2. By symmetry the total force on the pair of molecules F1 + F2 is downward (negative z direction).
The problem is that I do not get the mass movement. i'm checking the boundary conditions, but no obtain movement.
Thanks Ivar. With reference to attach file, consider a dielectric mass with two electrodes fixed to its surface. This construction is held at some small distance from a second dielectric mass which we wish to control. Imagine two molecules in the target dielectric placed symmetrically about the mid plane of the diagram. Creating a potential difference across the electrodes gives rise to a fringing field which polarises these molecules. Since the electric field is non-uniform the forces acting on the the positive and negative charges are not quite collinear leading to a resultant force on each molecule F1, F2. By symmetry the total force on the pair of molecules F1 + F2 is downward (negative z direction). The problem is that I do not get the mass movement. i'm checking the boundary conditions, but no obtain movement.

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