In order to account for consumption or production of the different phases due to one or more reactions or other physical processes, the Mass Source node adds source terms to the right-hand side of the phase transport equations.

Select the Mass transfer to other phases checkbox if mass is transferred from or to phases not accounted for in the phase transport interface, for instance when mass is released or absorbed by the solid part of the porous matrix. In this case the mass source for the phase calculated from the volume constraint should also be specified. The net mass transfer corresponds to the sum of the mass sources for all phases and should be accounted for in the computation of the flow field. When the Phase Transport in Porous Media interface is coupled to a Darcy’s Law interface using a Multiphase Flow in Porous Media multiphysics coupling node, this is done automatically.