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random motion of a sphere in 3D space

Posted Aug 5, 2021, 2:28 p.m. EDT Electromagnetics, Low-Frequency Electromagnetics Version 5.6 2 Replies

HP Doctoral student, Uppsala University
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hi,

I need to simulate a random motion of a small conducting sphere inside an air block.

I used stationary study and physics was electrostatics.

3 parameters were defined for x y z direction displacement and using parametric sweep I gave displacement for eac direction as randon(range(-1,0.1,1)). But it does not look correct.

Then I defined random function with 3 arguments and values were saved as text file. But now I could not assign values from text file to x y z displacements in moving mesh, prescribed deformation. (still I have not do any physics related steps)

Any comment on this issue?

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2 Replies Last Post Aug 11, 2021, 10:51 a.m. EDT
HP Doctoral student, Uppsala University
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Posted: 3 years ago Aug 8, 2021, 3:01 a.m. EDT

Hi, I managed to give random motion to the sphere using moving mesh(ALE). But while it is moving in air, sphere does not take material properties(copper). That is it became air. Is it a problem in geometry or moving mesh (ALE)?

I used 'assembly' under the geometry .

Hi, I managed to give random motion to the sphere using moving mesh(ALE). But while it is moving in air, sphere does not take material properties(copper). That is it became air. Is it a problem in geometry or moving mesh (ALE)? I used 'assembly' under the geometry .
Jeff Hiller COMSOL Employee

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Posted: 3 years ago Aug 11, 2021, 10:51 a.m. EDT
Updated: 1 year ago Apr 14, 2023, 9:57 a.m. EDT

Hello Hasupama,

Typically, in an electrostatic simulation like this one, you do not include perfect conductors like your copper sphere in the computational domain. Rather, you remove them from the geometry, so that the electric field is only solved for in the region occupied by the dielectric (air, in your case), and you apply a floating potential boundary condition at the surface of the perfect conductor (thereby ensuring that it is at a single, though not known a-priori, electric potential).

You don't need to use a moving mesh as far as I can tell if all you want to do is run a number of stationary studies each corresponding to a different location for the center of the sphere. A parametric sweep will do. See the attached file.

Best regards,

Jeff

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Jeff Hiller
Hello Hasupama, Typically, in an electrostatic simulation like this one, you do not include perfect conductors like your copper sphere in the computational domain. Rather, you remove them from the geometry, so that the electric field is only solved for in the region occupied by the dielectric (air, in your case), and you apply a floating potential boundary condition at the surface of the perfect conductor (thereby ensuring that it is at a single, though not known a-priori, electric potential). You don't need to use a moving mesh as far as I can tell if all you want to do is run a number of stationary studies each corresponding to a different location for the center of the sphere. A parametric sweep will do. See the attached file. Best regards, Jeff

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