Treatment of source term in the flow equation in ContactMechanicsBiot model

[jhabriel]

Hi,

I've noticed that in the treatment of the flow source term, a scaling with time-step is tacitly assumed, see:

porepy/src/porepy/models/contact_mechanics_biot_model.py

Line 835 in f68781e

- flow_source

Is this the intended treatment? Any particular reason why the scaling is not included explicitly, i.e.:

- ad.time_step * flow_source

I think this would be more consistent with the nature of the governing equations.

Moreover, it is not consistent with the implementation of SlightlyIncompressibleFlow, see:

porepy/src/porepy/models/slightly_compressible_flow_model.py

Line 84 in f68781e

def _assign_equations(self) -> None:

[IvarStefansson]

I think the answer has to do with the Biot class and the assembler version. My suggestion is that you make an issue on this and that we resolve it once we remove the assembler version of Models.