Discussion Forum

In the documentation under the topic "Physics Axial Symmetry Node" it says "The condition on the symmetry axis is typically a zero Neumann or no-flux condition.", but I'm wondering whether this is scaled by the conductivity in the Electric Currents interface.

Equation View doesn't show any equations for this node.

In my case, I have the conductivity in the radial direction equal to zero. But the convergence near the axis is poor, and I suspect that it's because there is a conflict:
• The PDE wants a certain kind of shape for the dependent variable field (voltage).
• The Axial Symmetry BC seems to be trying to get the slope of the voltage in the radial direction to be flat approaching the axis. (Even though the conductivity there is zero, i.e. no current flows.)

By the way, on this thread ( www.comsol.com/community/forums/general/thread/6598/ )
there is discussion that this partial derivative should be zero on an axis, which is true in most cases, but not in my case (i.e. when the conductivity is zero, the flux is always zero, whatever the gradient, and the condition always holds). It seems to me that "Axial Symmetry" is trying to constrain the gradient, rather than the flux.

But I've ran out of ways I know of figuring out exactly what Axial Symmetry BC is doing...



                                                                                                                                                                                                         -- Evgeni.org