Test on an idealized geometry 

Diagnostic equations:
To launch this test, use runme

tests 3 and 4:
A=5.7*10^-19 Pa^-3.a^-1 -> B=1.7687*10^8 Pa.s^1/3

density 5100 -> 1488 nodes and 2839 elements
dentity 3550 -> 3221 nodes and 6232 elements
