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Addition of gravity force in AC/DC module

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Hello,
I need your help. I have to include the gravity force in my model of permanent ring magnet, which is stand on the iron surface. In my model I compute a magnetic force wchich I need to pull the iron surface to magnet.

Thank you for any help

Krystian


2 Replies Last Post 2010年11月11日 GMT-5 11:40
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2010年11月10日 GMT-5 02:33
Hi

I'm not sue I understand, gravity forces exist in structural, but are not defined by default in ACDC, as F[N]=m[kg]*G[m/s^2] and the mass m is the sum over the domains of their densities, times the domain integral of 1*dVolume you should evaluate the mass and multiply by g_const, COMSOL internal value for G and add that to the correct coordinate direction, no?

Or you need to couple the structural physics, add a body load solid.rho*g_const, and add the magnetic forces as external imported forces

--
Good luck
Ivar
Hi I'm not sue I understand, gravity forces exist in structural, but are not defined by default in ACDC, as F[N]=m[kg]*G[m/s^2] and the mass m is the sum over the domains of their densities, times the domain integral of 1*dVolume you should evaluate the mass and multiply by g_const, COMSOL internal value for G and add that to the correct coordinate direction, no? Or you need to couple the structural physics, add a body load solid.rho*g_const, and add the magnetic forces as external imported forces -- Good luck Ivar

Ruud Borger COMSOL Employee

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Posted: 1 decade ago 2010年11月11日 GMT-5 11:40
Hello,

Ivar's advice is sound: the best idea is to set up your AC/DC model, then add a Solid Mechanics Physics Set. Now set a Volume Force to the appropriate domain where your force is the sum of the gravity and the other force calculated in the AC/DC physics set. You can look up the name of this force in the results node or under "View equations".

Good luck!

Hello, Ivar's advice is sound: the best idea is to set up your AC/DC model, then add a Solid Mechanics Physics Set. Now set a Volume Force to the appropriate domain where your force is the sum of the gravity and the other force calculated in the AC/DC physics set. You can look up the name of this force in the results node or under "View equations". Good luck!

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