Creating Pathway Networks

A model of an environmental system is created by linking pathway elements together into a pathway network, as shown below:

GoldSim moves mass through the network, keeping track of the temporally varying amount of mass in each pathway.

To create such a network, individual pathways are connected via mass flux links. A mass flux link An interconnnection between two transport pathways that defines the rate at which species move between the pathways. controls the rate at which 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). are moving between pathways. The mass flux is a vector A one-dimensional array. by species (i.e., it has one item for each species), since the flux will differ for each species being simulated, and has dimensions An output attribute for an element that defines the dimensionality (in terms of Length, Time and other fundamental dimensions) of the output. of mass/time.

Note: The Contaminant Transport Module relies heavily on GoldSim's ability to create and manipulate vectors.

Two major types of mass flux links and three special purpose mass flux links can be defined in GoldSim. In an advective mass flux link A mass flux link in which a quantity of a medium is specified to flow from one pathway to another, carrying dissolved, sorbed, and/or suspended species with it., a quantity of a medium is specified to flow from one pathway to another, carrying dissolved, sorbed, and/or suspended species with it. In a diffusive mass flux link A mass flux link in which species diffuse between pathways according to a concentration gradient., species diffuse between pathways according to a concentration gradient. Three special purpose mass flux links allow you to model processes that cannot be represented as using advection of diffusion. In a direct transfer mass flux link, species are moved from one pathway to another based on a user-specified transfer rate. In a precipitate removal mass flux link, species present as precipitated mass are moved from one pathway to another based on a specified transfer rate. In a treatment mass flux link A mass flux link in which species are filtered (treated) as they are moved from one pathway to another based on a user-specified fraction (treatment efficiency)., species are treated or filtered and are moved to from one pathway to another based on a specified treatment efficiency (a fraction).

Based on the properties of each pathway, the media Materials (such as water, sand, clay, air) that constitute (are contained within) transport pathways. GoldSim provides two types of elements for defining media: Fluids and Solids. in each pathway, the species, and the specified mass flux links, GoldSim computes the amount of mass in each pathway, the concentrations in each pathway's media, and the mass fluxes between pathways, all of which vary with time. Hence, the fundamental output of a pathway element is a series of vectors: the mass (of each species) in the pathway, the mass flux (of each species) to each of the pathways to which it is connected via mass flux links, and the concentrations (of each species) within the environmental media in the pathway.