Hi all,

I would like to add gravity body force, b_i, into biot.py:

The body force, b_i, in balance equation can be expressed by 

(\sigma_{ij} - p \delta_{ij}),j +  \rho b_i  = 0

where \sigma_{ij} is stress, p is pore pressure and \rho is the density of solid phase.

\delta_{ij} is Kronecker delta.

Should I add a new term from scratch?

Thanks in advance.

ouyang