Mass Nodal Sink/Source BC

Unit: [M/T]

A nodal sink or source boundary condition for mass transport applies a predefined extraction or injection of a solute to a node.

Nodal sink/source boundary conditions are applied in cases where the injection/abstraction of mass at a certain location is known.

For defining boundary conditions, inflows are considered as negative, outflows as positive. Thus a nodal sink/source boundary condition with a positive sign means removal of mass, negative signs are used for adding mass.

The meaning of a mass nodal sink/source BC depends on whether the convective or divergence form of the transport equation is used.
In most practical cases, the usage of this type of boundary condition is to be avoided in combination with the (default) convective form if there is a flow boundary condition on the same node. A mass- concentration boundary condition is to be preferred in these cases.