General Information Flow to and from an External Pathway

Before describing how you specify the properties of an External pathway A transport pathway element that provides a mechanism by which external program modules for contaminant transport (e.g., analytical, finite elelement, or finite difference models) can be directly integrated into GoldSim., it is useful to summarize the general information flow between GoldSim and the External pathway function.

The following information is automatically passed by GoldSim to the External pathway function when it is called:

• any (optional) input arguments that you wish to send to the function (you will always need to pass the current time, but need not send any additional inputs);
• the number of species The chemical (or non-chemical, such as bacterial or viral) constituents that are stored and transported through an environmental system in a contaminant transport model. In GoldSim, the Species element defines all of the contaminant species being simulated (and their properties). in the model;
• the number of mass flux links into the pathway;
• the number of mass flux links which GoldSim expects to be returned from the pathway;
• a flag indicating whether all species fluxes in the mass flux links into the pathways are zero for the current call (which you could use to internally instruct the External pathway to skip various calculations); and
• a vector A one-dimensional array. for each mass flux link An interconnnection between two transport pathways that defines the rate at which species move between the pathways. into the External pathway indicating the quantity of mass of each species passed to the External pathway since the last time it was called (typically one timestep A discrete interval of time used in dynamic simulations.).

GoldSim expects the following information to be returned from the External pathway function when it is called:

• any (optional) output arguments that you wish to return from the function (you need not return any additional outputs);
• a vector for each mass flux link out of the External pathway indicating the quantity of mass of each species passed from the External pathway since the last time it was called (typically one timestep).

The details regarding the manner in which this information is passed is provided in Appendix C of the Contaminant Transport Module User’s Guide.