Simulation crashes at high tolerance
 

Dear Foamers,

When I run a transport equation (Poisson Nernst Planck equation) with AC electric field as boundary conditions, I see that the simulation works fine when the tolerances are set to 7e-7, but when I run the case with tolerance 1e-11 the code crashes after some time step. What could be the reason for this behavior.

Kindly let me know.

Thanks