Discussion Forum

My colleague and I have been struggling with COMSOL modeling recently. Specifically, COMSOL seems to calculate forces that should be symmetrical to be assymetrical about a zero point.

In my case, I am calculating the torque on a 2D triangular particle suspended in a liquid medium over a gap between biased electrode digits (on the x-y plane running parallel to the y axis) as a function of the rotation of the particle in the x-z plane using DC model (please see the attached .gif). The particle is centered over the biased gap, and lying parallel to the electrode surface is defined as having 0 rotation. As the particle is rotated about its axis parallel to the electrode edges ( the y-axis), the torque on the particle about this axis should be symmetrical about its original position (flat), but in opposite directions (opposite signs).

However, Comsol outputs a torque that is asymmetrical about zero rotation and is always positive (torque is only in one direction). I believe these are artifacts of the modeling because the torque profile did not change when I switched the bias on the electrode digits. In addition, I tested the symmetry using a flat square particle with obvious geometrical symmetry, and obtained similarly asymmetrical results.

I have been using custom meshing with small elements and low growth rate, so I don't believe that to be the issue, but any help is appreciated.

Thank you in advance,

Donna