Prior to sending the mass flux data to the External pathway function, GoldSim converts the mass flux vectors to mass vectors. These represent the amount of mass (of each species) moving through the link since the last time the External pathway function was called. The External pathway function returns the mass flux data in the same form. GoldSim converts these mass vectors to and from mass fluxes by dividing by the amount of time since the last function call.
The portion of the External pathway dialog labeled "Mass Transport" contains three inputs which control the manner in which mass flux data is passed between GoldSim and the External pathway function:
Combine flux inputs to pathway: If this box is checked, GoldSim will combine the mass fluxes for all mass flux links to the External pathway into a single vector and pass this to the External pathway function. If the checkbox is cleared, the mass flux links are passed separately to the External pathway function in the order they are defined (i.e., the order they are displayed in the Inflows tab).
Split single flux output from pathway: If this box is checked, GoldSim assumes that a single mass vector will be passed from the External pathway function back to GoldSim. GoldSim then distributes the mass to the specified pathway Outflows in proportion to the specified flow rates for the links. If the checkbox is cleared, GoldSim expects that the External pathway function will pass a separate vector for each specified Outflow in the order they are defined (i.e., the order they are displayed in the Outflows tab).
Mass Units: These are the mass units that the External pathway function expects to receive (and return) mass flux data. GoldSim converts the mass vectors into these units prior to sending them to the External pathway function, and converts the returning mass vectors from these units (to the internal system units) after receiving them from the function.