computing accurate fluxes with periodic boundary conditions?

Hi everybody,

does anyone know if I can compute the fluxes accurately, as described in the user guide on page 308 ff. and file 0973 from the knowdledge database etc, when using periodic boundary conditions on the respective boundaries? In the descriptions, it is explained only for Dirichlet boundary conditions :( And if you think it should work, should I then use the weak constraint option? (and, how, if you have time to explain?) I model in the PDE mode of version 4.1. with matlab.

All best,
Sabine