Discussion Forum

Greetings,

I am currently attempting to model a solid cylinder in a hollow cylinder, where there is a gap (very small gap about 1e-5 m) and it is a 2d cut perpendicular to the cylinders axis. I am running in to a problem of, as i heat the inner cylinder it undergoes thermal expansion and the outer cylinder is undergoing creep down from an external pressure and the inner cylinders temperature. This gap has some conductivity which i know its behaviour as a function of gap thickness, but eventually this gap will disappear and thermal conductivity will be dominated by contact.

My questions are:

How can i make this gap disappear, I have to mesh it to give it some thermal conductivity and for it to contribute some force against the expansion, so if I have the gas shrink to the point of non existence i would get some mesh deformation. In reality the gas would compress elsewhere (the problem is really three D i am attempting a simpler method. So what is the best way to model this gap?

Also how do i make comsol use gap thickness dependent data?

is there any tricks to get a pseudo thermal conduction without meshing the gap? (as it is just the heat transfer i cant think of a way around but the pressure i can?