paste squeeze simulation advice

[mark smith]

Hi Elmer group,
Referring to the image below maybe someone can offer advice on how to simulate the following 3D problem with Elmer (if possible) or any other tool they might know of that could do it.

problem image

test_problem.png (9.43 KiB) Viewed 2317 times

A bead or beads (even dots) of paste (properties known) of given thickness and shape are applied to the substrate, A component of given size & shape is then lowered onto the bead and displaced to squeeze the paste between the 2 surfaces (not necessarily flat or planar) to a particular thickness, I want to calculate how the shape of the squeezed paste changes as the displacement is increased, so I can optimize the shape and pattern of the bead/s to minimize the outflow around the edge of the component and prevent any air voids being trapped between individual islands of paste.

My first thought is of a fluid/structure interaction problem with 2 phase flow using the level-set method but as far as I know Elmer's level set is limited to 2D problems only, so I am looking for an alternative approach or methodology?

Thanks in advance
Best regards
Mark

[raback]

Hi Mark

This is indeed quite a tricky problem. Basically the levelset method can deal with 3D problems except that the some reinitialization of the levelset function (signed distance) is implemented only in 2D. The PDE based reinitialization should work though. That being said I would not be too optimistic that it would work that well for this problem. Levelset method would be better suited if the other substance (air) would be similar in properties. Also the no-slip conditions for the paste tend to cause some problems because that means that levelset function will not be convected there. So at least some kind of slip conditions, or some other tricks, would be needed to properly follow the paste front.

-Peter