This problem describes the flow through an anisotropic porous foundation.
It is taken from Zienkiewicz, "The Finite Element Method in Engineering Science",
title 'Anisotropic Porous flow'
ky = 1
kx = 4
pressure : dx(kx*dx(pressure)) + dy(ky*dy(pressure)) = 0
natural(pressure)=0 line to (5,0) to (5,5)
value(pressure)=0 line to (2,2)
natural(pressure)=0 line to (2.5,2) to (2.5,1.95) to (1.95,1.95)
value(pressure)=100 line to close