Calculation of DupuitPermeability using aquifer thickness
Description
Currently DupuitPermeability is calculated by multiplying the permeability by the actual pressure whereas pressure should represent values of hydraulic head. The effect is that fluxes increase with increasing pressure. However, looking on real-world applications in hydrogeology, the value of DupuitPermeability can only increase until the upper_bound of an (unconfined) aquifer is filled by water. A further increase of hydraulic head should not have any impact on DupuitPermeability as excess water leaves the porous media. One solution could be to constrain the calculation of DupuitPermeability by providing property meshes for both the lower and upper aquifer boundaries
I created a small example set-up with a hypothetical maximum aquifer thickness of 1m. In the "flooded case", calculated velocities would be constant over the entire domain (similar to LIQUID_FLOW output), if a constrain on DupuitPermeability was defined