Selecting interior surface only of enclosed region

[eyeguy]

Hello,

I've lurked here for a while, but finally signed up to ask a question. I'm not sure if it's easy/hard/impossible, but I seem to be stumped with a relatively simple problem:

I'm modeling the tissue of an eye in ANSYS using a mesh generated from MRI data (therefore no mapped meshing). I need to apply a pressure to the interior surface of the eye to simulate the intraocular pressure (think of air inside a balloon pushing outwards). My problem is that doing something like an nsel with the ext component grabs nodes on both the interior and exterior of the eye model, rather than just the interior. Currently the only way I can think of doing it is with a painstaking series of math-based subtractions, but that's neither quick nor accurate. Any ideas?

 

[ansysfreak]

Hi

What type of element do you use?? If you use an shell element you can only select nodes that are int. and ext.

Grtz
Garry

 

[meshparts]

Hi,

I woul try to define a polar coordinate system in the mass center of the eye. Then select nodes on exterior and then reselect node in a specified range of radius:

local,1000,2,...
nsel,s,ext
nsel,r,loc,x,rad_min,rad_max

Regards,
Alex

 

[eyeguy]

I currently am using SOLID45 tetrahedral elements, as the MRI meshes are tetrahedral when outputted. As far as I know, there's no easy way to move over to shell from this, correct?

Mihaiupb, that's kind of what I'm thinking at this point too. Unfortunately real human eyes aren't exactly spherical, so it may take a bit more work.

Thanks for the replies so far.