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Improving Output of Slow Time Dependent Study

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Hello,

I am relativly new to COMSOL, and although I have experience working with Stationary studies, I am now attempting to use a Time Dependent study to model the displacement of a small bead (0.25mm radius) embedded in a big block of gelatin when the bead is subject to a sinusoidally-modulated body load. This is a nice build-up toward what I want to do since in this case, I actually have an analytical model of what the displacement should look like.

As you can see in the attached image though, things aren't going quite as planned. With a "normal" mesh, the solution exhibits a weird blocky behavior, and does not make it up to the proper displacement amplitude. I can increase the mesh size to Extra fine to fix the second problem (at the cost of hours of computation time) but the same blocky behavior still exists. I have also tried decreasing the tolerance by several orders of magnitude. While this does slow down the simulation considerably, the solution is ultimatly the same leading me to conclude that this is not a time sampling issue. The physics here don't seem super complicated -- it's a very small displacement in a gelatin block that is 4 orders of magnitude larger than the displacement. Furthermore the sine wave is very slow -- the period if 5 seconds.

Would someone be kind enough to help me understand what's going on and how I might attempt to fix it?

Thank you!



0 Replies Last Post 24.10.2020, 09:29 GMT-4
COMSOL Moderator

Hello Ben Levy

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