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Moving Mesh - Position = Dependent Variable

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I have a spherical shell. I want to make its inner radius R1 and outer radius R2 move over time (just radially, like a ball getting bigger). I don't know how to tell COMSOL to move the radius. I know I must use the ALE method and I already have the "Moving Mesh" pack. I tried two ways of doing this, none worked:

1.-I first tried to go to Set "Prescribed Mesh Displacement" and set each surface with corresponding radial position (R1 or R2). This doesn't work for me because when I get to that option, I try to choose boundaries and it just tells me: "1(not applicable)", "2(not applicable)" and so on for all surfaces.

2.- Then, I tried with velocities, I could specify surface velocities on each surface, I used the option: "Prescribed Mesh Velocity", and this should do the job, but I don't know how to set velocity = time derivative of dependent function. How can I do this?

I am using COMSOL 4.0

If anyone could tell me how to set velocity = time derivative of dependent function, or if anyone could tell me how to get the boundaries to not say "not applicable", it would be awesome. I am attaching my model, but it doesn't run yet because it is a work in progress.


2 Replies Last Post 26 dic 2011, 15:17 GMT-5

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Posted: 1 decade ago 25 dic 2011, 08:15 GMT-5
Anyone knows how to do this?
Anyone knows how to do this?

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Posted: 1 decade ago 26 dic 2011, 15:17 GMT-5
You need to define "free deformation" node and select your domain. Then the boundaries become accessible.
You need to define "free deformation" node and select your domain. Then the boundaries become accessible.

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