Defining subdomains for two different materials


How I can defining subdomains for two different materials ?

This can either be done with a geometrical description, as shown in this tutorial: https://fenicsproject.org/docs/dolfin/1.4.0/python/demo/documented/subdomains-poisson/python/documentation.html

You can Also use a gmesh to define the cell function, and load it as described here:

Thank you very much.