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I am fairly new to COMSOL and was wondering of anyone knows how to correctly define a floating electrode in a 2D simulation? I have some strange results from my simulation.

I have two concentric electrodes - one at an arbitrary voltage and one earthed. Between them is an insulation layer with an embedded cylindrical electrode at floating potential.

I have tried defining the embedded electrode as either at a floating potential or a terminal with 0A current, but I always get wrong results, with the electrode behaving as if it's connected to 0V instead of ending up at a floating potential of some voltage between 0 and the supply.

For this setup, the electric field will induce a -ve charge on the side of the floating electrode facing it. On the other side of the floating electrode, a +ve charge should be left, which also enhances the field, but it should be in the same direction as it was on the first side of the electrode, since it is flux going from this positive induced charges towards a more -ve outer earth electrode.

However, my simulation the electric fields are opposite in magnitude on either side of the floating electrode. There is either something wrong with the boundary conditions or simulation type but I can't figure out what. (Does the electrode have infinite capacitance so it can't reach a potential, or should the simulation be something other than stationary?)

Any suggestions?

Thanks

AR