Adds a conservation equation for polymer.
Polymer concentration in the water phase is used as primary variable
The polymer influences the viscosity of the water, and leaves gas and oil
uneffected.
A shear multiplier is computed if PLYSHLOG and/or SHRATE is specified
based on either velocity or shrate.
The shear multiplier effects the water and polymer viscosity.
Tested and verified on the test cases in polymer_test_suite
Conceptually this is IMO pretty questionable, since it adds a second
"gas phase" that does not mix with "ordinary" gas. I suppose the
reason why this extension was conceived by E100 is that if all you
have is hammer, everything looks like a nail...
Functionality-wise, this patch is still not fully complete because
miscibility of the solvent "phase" is not yet implemented. As far as I
can see, the API changes required by miscibility are quite limited,
though.
let's use zero instead of 10^-18. This can have a small impact on
performance, but the new version is definitely "more" correct, and
also Norne performance seems to improve slightly on my machine.
before, they were undefined for phases which exhibited zero mobility
in both directions. since in this case the flux is zero (and thus the
upstream direction does not matter), the correctness is unaffected by
this patch. (still, I consider it to bug and valgrind also complained
about it.)
