J "solid.J*J0" "Swelling volume ratio" Psi_s "G/(2*J0)*(stretch0^2*solid.I1Cel-3-2*log(J0*solid.Jel))" "Free energy of stretching" Psi_mix "-Kmix*((solid.Jel-J0^(-1))*log(J0*solid.Jel/(J0*solid.Jel-1))+chi/(J0^2*solid.Jel))" "Free energy of mixing" Kdef "(solid.J-J0^(-1))*kappa0" "Deformation-dependent permeability" KRR "Kdef*solid.Cil11" "Permeability, RR component" KRZ "Kdef*solid.Cil13" "Permeability, RZ component" KZZ "Kdef*solid.Cil33" "Permeability, ZZ component"