I have some problem in electrostatic coupled-field analsys.

I have a MEMS capacitive actuator which incorporates irregulator shapes of air. I use 2D simulation now.

Is it always necessary to set the edge to air to UX,UY to zero?

I sometimes observed very weird large deformation of air. If I do not define the edge of air to UX,UX zero, the deformed shape sometimes show that the inside node will leave away from the air material.

Thanks!